The ability to detect sharp boundaries (stimuli) and to detect slight changes in luminance at regions without distinct contours. Psychophysical measurements of this visual function are used to evaluate visual acuity and to detect eye disease.
Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.
A series of tests used to assess various functions of the eyes.
Relatively bright light, or the dazzling sensation of relatively bright light, which produces unpleasantness or discomfort, or which interferes with optimal VISION, OCULAR. (Cline et al., Dictionary of Visual Science, 4th ed)
The minimum amount of stimulus energy necessary to elicit a sensory response.
A nonspecific term referring to impaired vision. Major subcategories include stimulus deprivation-induced amblyopia and toxic amblyopia. Stimulus deprivation-induced amblyopia is a developmental disorder of the visual cortex. A discrepancy between visual information received by the visual cortex from each eye results in abnormal cortical development. STRABISMUS and REFRACTIVE ERRORS may cause this condition. Toxic amblyopia is a disorder of the OPTIC NERVE which is associated with ALCOHOLISM, tobacco SMOKING, and other toxins and as an adverse effect of the use of some medications.
Visual impairments limiting one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from EYE DISEASES; OPTIC NERVE DISEASES; VISUAL PATHWAY diseases; OCCIPITAL LOBE diseases; OCULAR MOTILITY DISORDERS; and other conditions (From Newell, Ophthalmology: Principles and Concepts, 7th ed, p132).
The science dealing with the correlation of the physical characteristics of a stimulus, e.g., frequency or intensity, with the response to the stimulus, in order to assess the psychologic factors involved in the relationship.
Function of the human eye that is used in dim illumination (scotopic intensities) or at nighttime. Scotopic vision is performed by RETINAL ROD PHOTORECEPTORS with high sensitivity to light and peak absorption wavelength at 507 nm near the blue end of the spectrum.
Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)
The process in which light signals are transformed by the PHOTORECEPTOR CELLS into electrical signals which can then be transmitted to the brain.
Mental processing of chromatic signals (COLOR VISION) from the eye by the VISUAL CORTEX where they are converted into symbolic representations. Color perception involves numerous neurons, and is influenced not only by the distribution of wavelengths from the viewed object, but also by its background color and brightness contrast at its boundary.
Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity.
Defects of color vision are mainly hereditary traits but can be secondary to acquired or developmental abnormalities in the CONES (RETINA). Severity of hereditary defects of color vision depends on the degree of mutation of the ROD OPSINS genes (on X CHROMOSOME and CHROMOSOME 3) that code the photopigments for red, green and blue.
The total area or space visible in a person's peripheral vision with the eye looking straightforward.
Mental process to visually perceive a critical number of facts (the pattern), such as characters, shapes, displays, or designs.
The awareness of the spatial properties of objects; includes physical space.
The point or frequency at which all flicker of an intermittent light stimulus disappears.
Set of cell bodies and nerve fibers conducting impulses from the eyes to the cerebral cortex. It includes the RETINA; OPTIC NERVE; optic tract; and geniculocalcarine tract.
The electric response evoked in the cerebral cortex by visual stimulation or stimulation of the visual pathways.
The sensory discrimination of a pattern shape or outline.
An area approximately 1.5 millimeters in diameter within the macula lutea where the retina thins out greatly because of the oblique shifting of all layers except the pigment epithelium layer. It includes the sloping walls of the fovea (clivus) and contains a few rods in its periphery. In its center (foveola) are the cones most adapted to yield high visual acuity, each cone being connected to only one ganglion cell. (Cline et al., Dictionary of Visual Science, 4th ed)
The study and treatment of defects in binocular vision resulting from defects in the optic musculature or of faulty visual habits. It involves a technique of eye exercises designed to correct the visual axes of eyes not properly coordinated for binocular vision.
The adjustment of the eye to variations in the intensity of light. Light adaptation is the adjustment of the eye when the light threshold is increased; DARK ADAPTATION when the light is greatly reduced. (From Cline et al., Dictionary of Visual Science, 4th ed)
The aperture in the iris through which light passes.
The blending of separate images seen by each eye into one composite image.
Type of vision test used to determine COLOR VISION DEFECTS.
A refractive error in which rays of light entering the EYE parallel to the optic axis are brought to a focus in front of the RETINA when accommodation (ACCOMMODATION, OCULAR) is relaxed. This results from an overly curved CORNEA or from the eyeball being too long from front to back. It is also called nearsightedness.
Function of the human eye that is used in bright illumination or in daylight (at photopic intensities). Photopic vision is performed by the three types of RETINAL CONE PHOTORECEPTORS with varied peak absorption wavelengths in the color spectrum (from violet to red, 400 - 700 nm).
Misalignment of the visual axes of the eyes. In comitant strabismus the degree of ocular misalignment does not vary with the direction of gaze. In noncomitant strabismus the degree of misalignment varies depending on direction of gaze or which eye is fixating on the target. (Miller, Walsh & Hoyt's Clinical Neuro-Ophthalmology, 4th ed, p641)
Artificial implanted lenses.
Partial or complete opacity on or in the lens or capsule of one or both eyes, impairing vision or causing blindness. The many kinds of cataract are classified by their morphology (size, shape, location) or etiology (cause and time of occurrence). (Dorland, 27th ed)
Vision considered to be inferior to normal vision as represented by accepted standards of acuity, field of vision, or motility. Low vision generally refers to visual disorders that are caused by diseases that cannot be corrected by refraction (e.g., MACULAR DEGENERATION; RETINITIS PIGMENTOSA; DIABETIC RETINOPATHY, etc.).
Differential response to different stimuli.
Part of the DIENCEPHALON inferior to the caudal end of the dorsal THALAMUS. Includes the lateral geniculate body which relays visual impulses from the OPTIC TRACT to the calcarine cortex, and the medial geniculate body which relays auditory impulses from the lateral lemniscus to the AUDITORY CORTEX.
Method of measuring and mapping the scope of vision, from central to peripheral of each eye.
A specialized field of physics and engineering involved in studying the behavior and properties of light and the technology of analyzing, generating, transmitting, and manipulating ELECTROMAGNETIC RADIATION in the visible, infrared, and ultraviolet range.
The selecting and organizing of visual stimuli based on the individual's past experience.
Normal nystagmus produced by looking at objects moving across the field of vision.
A pair of ophthalmic lenses in a frame or mounting which is supported by the nose and ears. The purpose is to aid or improve vision. It does not include goggles or nonprescription sun glasses for which EYE PROTECTIVE DEVICES is available.
The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.
A surgical procedure to correct MYOPIA by CORNEAL STROMA subtraction. It involves the use of a microkeratome to make a lamellar dissection of the CORNEA creating a flap with intact CORNEAL EPITHELIUM. After the flap is lifted, the underlying midstroma is reshaped with an EXCIMER LASER and the flap is returned to its original position.
Cognitive disorders characterized by an impaired ability to perceive the nature of objects or concepts through use of the sense organs. These include spatial neglect syndromes, where an individual does not attend to visual, auditory, or sensory stimuli presented from one side of the body.
A localized defect in the visual field bordered by an area of normal vision. This occurs with a variety of EYE DISEASES (e.g., RETINAL DISEASES and GLAUCOMA); OPTIC NERVE DISEASES, and other conditions.
Adjustment of the eyes under conditions of low light. The sensitivity of the eye to light is increased during dark adaptation.
Inflammation of the optic nerve. Commonly associated conditions include autoimmune disorders such as MULTIPLE SCLEROSIS, infections, and granulomatous diseases. Clinical features include retro-orbital pain that is aggravated by eye movement, loss of color vision, and contrast sensitivity that may progress to severe visual loss, an afferent pupillary defect (Marcus-Gunn pupil), and in some instances optic disc hyperemia and swelling. Inflammation may occur in the portion of the nerve within the globe (neuropapillitis or anterior optic neuritis) or the portion behind the globe (retrobulbar neuritis or posterior optic neuritis).
Awareness of oneself in relation to time, place and person.
The illumination of an environment and the arrangement of lights to achieve an effect or optimal visibility. Its application is in domestic or in public settings and in medical and non-medical environments.
Refraction of LIGHT effected by the media of the EYE.
A species of the genus MACACA which inhabits Malaya, Sumatra, and Borneo. It is one of the most arboreal species of Macaca. The tail is short and untwisted.
Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus.
Images seen by one eye.
The dioptric adjustment of the EYE (to attain maximal sharpness of retinal imagery for an object of regard) referring to the ability, to the mechanism, or to the process. Ocular accommodation is the effecting of refractive changes by changes in the shape of the CRYSTALLINE LENS. Loosely, it refers to ocular adjustments for VISION, OCULAR at various distances. (Cline et al., Dictionary of Visual Science, 4th ed)
The real or apparent movement of objects through the visual field.
Area of the OCCIPITAL LOBE concerned with the processing of visual information relayed via VISUAL PATHWAYS.
Photosensitive afferent neurons located primarily within the FOVEA CENTRALIS of the MACULA LUTEA. There are three major types of cone cells (red, blue, and green) whose photopigments have different spectral sensitivity curves. Retinal cone cells operate in daylight vision (at photopic intensities) providing color recognition and central visual acuity.
Processes and properties of the EYE as a whole or of any of its parts.
That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.
Degenerative changes in the RETINA usually of older adults which results in a loss of vision in the center of the visual field (the MACULA LUTEA) because of damage to the retina. It occurs in dry and wet forms.
An ocular disease, occurring in many forms, having as its primary characteristics an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function. The consequences of the increased pressure may be manifested in a variety of symptoms, depending upon type and severity, such as excavation of the optic disk, hardness of the eyeball, corneal anesthesia, reduced visual acuity, seeing of colored halos around lights, disturbed dark adaptation, visual field defects, and headaches. (Dictionary of Visual Science, 4th ed)
A cognitive disorder characterized by an impaired ability to comprehend written and printed words or phrases despite intact vision. This condition may be developmental or acquired. Developmental dyslexia is marked by reading achievement that falls substantially below that expected given the individual's chronological age, measured intelligence, and age-appropriate education. The disturbance in reading significantly interferes with academic achievement or with activities of daily living that require reading skills. (From DSM-IV)
Persons with loss of vision such that there is an impact on activities of daily living.
Perception of three-dimensionality.
Application of tests and examinations to identify visual defects or vision disorders occurring in specific populations, as in school children, the elderly, etc. It is differentiated from VISION TESTS, which are given to evaluate/measure individual visual performance not related to a specific population.
A condition of an inequality of refractive power of the two eyes.
The positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye.
The absence or restriction of the usual external sensory stimuli to which the individual responds.
The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.
Glaucoma in which the angle of the anterior chamber is open and the trabecular meshwork does not encroach on the base of the iris.
A long-acting injectable antipsychotic agent used for chronic schizophrenia.
Measurement of the various properties of light.
Unequal curvature of the refractive surfaces of the eye. Thus a point source of light cannot be brought to a point focus on the retina but is spread over a more or less diffuse area. This results from the radius of curvature in one plane being longer or shorter than the radius at right angles to it. (Dorland, 27th ed)
The function of the eye that is used in the intermediate level of illumination (mesopic intensities) where both the RETINAL ROD PHOTORECEPTORS and the RETINAL CONE PHOTORECEPTORS are active in processing light input simultaneously.
Lenses designed to be worn on the front surface of the eyeball. (UMDNS, 1999)
The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)
An alternative to REFRACTIVE SURGICAL PROCEDURES. A therapeutic procedure for correcting REFRACTIVE ERRORS. It involves wearing CONTACT LENSES designed to force corrective changes to the curvature of the CORNEA that remain after the lenses are removed. The effect is temporary but is maintained by wearing the therapeutic lenses daily, usually during sleep.
Continuation of visual impression after cessation of stimuli causing the original image.
The study of the physiological basis of human and animal behavior.
Conditions which produce injury or dysfunction of the second cranial or optic nerve, which is generally considered a component of the central nervous system. Damage to optic nerve fibers may occur at or near their origin in the retina, at the optic disk, or in the nerve, optic chiasm, optic tract, or lateral geniculate nuclei. Clinical manifestations may include decreased visual acuity and contrast sensitivity, impaired color vision, and an afferent pupillary defect.
Theoretical representations that simulate psychological processes and/or social processes. These include the use of mathematical equations, computers, and other electronic equipment.
The use of an aberrometer to measure eye tissue imperfections or abnormalities based on the way light passes through the eye which affects the ability of the eye to focus properly.
'Ethylamines' are organic compounds containing an ethyl group (two carbon atoms) bonded to an amino group (-NH2), which can vary in their complexity and properties, playing a role in various biological processes or utilized in the synthesis of numerous pharmaceuticals and chemicals.
The removal of a cataractous CRYSTALLINE LENS from the eye.
The sensory interpretation of the dimensions of objects.
Neurons of the innermost layer of the retina, the internal plexiform layer. They are of variable sizes and shapes, and their axons project via the OPTIC NERVE to the brain. A small subset of these cells act as photoreceptors with projections to the SUPRACHIASMATIC NUCLEUS, the center for regulating CIRCADIAN RHYTHM.
Argon. A noble gas with the atomic symbol Ar, atomic number 18, and atomic weight 39.948. It is used in fluorescent tubes and wherever an inert atmosphere is desired and nitrogen cannot be used.
The effect of environmental or physiological factors on the driver and driving ability. Included are driving fatigue, and the effect of drugs, disease, and physical disabilities on driving.
The visually perceived property of objects created by absorption or reflection of specific wavelengths of light.
An exudate between the RETINA and CHOROID from various sources including the vitreous cavity, SUBARACHNOID SPACE, or abnormal vessels.
The system of all phenomena in space and time; the totality of physical reality. It is both a scientific and philosophic concept appearing in all historic eras. (Webster 2d; Dr. James H. Cassedy, NLM History of Medicine Division)
The normal decreasing elasticity of the crystalline lens that leads to loss of accommodation.
The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.
Surgical procedures employed to correct REFRACTIVE ERRORS such as MYOPIA; HYPEROPIA; or ASTIGMATISM. These may involve altering the curvature of the CORNEA; removal or replacement of the CRYSTALLINE LENS; or modification of the SCLERA to change the axial length of the eye.
Recording of electric potentials in the retina after stimulation by light.
Elements of limited time intervals, contributing to particular results or situations.
Retinal diseases refer to a diverse group of vision-threatening disorders that affect the retina's structure and function, including age-related macular degeneration, diabetic retinopathy, retinal detachment, retinitis pigmentosa, and macular edema, among others.
Disease of the RETINA as a complication of DIABETES MELLITUS. It is characterized by the progressive microvascular complications, such as ANEURYSM, interretinal EDEMA, and intraocular PATHOLOGIC NEOVASCULARIZATION.
The interference of one perceptual stimulus with another causing a decrease or lessening in perceptual effectiveness.
'Reading' in a medical context often refers to the act or process of a person interpreting and comprehending written or printed symbols, such as letters or words, for the purpose of deriving information or meaning from them.
A family of nonmetallic, generally electronegative, elements that form group 17 (formerly group VIIa) of the periodic table.
Absence of the crystalline lens resulting from cataract extraction.
Focusing on certain aspects of current experience to the exclusion of others. It is the act of heeding or taking notice or concentrating.
The concave interior of the eye, consisting of the retina, the choroid, the sclera, the optic disk, and blood vessels, seen by means of the ophthalmoscope. (Cline et al., Dictionary of Visual Science, 4th ed)
Devices for examining the interior of the eye, permitting the clear visualization of the structures of the eye at any depth. (UMDNS, 1999)
The administration of substances into the eye with a hypodermic syringe.
Insertion of an artificial lens to replace the natural CRYSTALLINE LENS after CATARACT EXTRACTION or to supplement the natural lens which is left in place.
Lack of correspondence between the way a stimulus is commonly perceived and the way an individual perceives it under given conditions.
A type of refractive surgery of the CORNEA to correct MYOPIA and ASTIGMATISM. An EXCIMER LASER is used directly on the surface of the EYE to remove some of the CORNEAL EPITHELIUM thus reshaping the anterior curvature of the cornea.
The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold.
The act of knowing or the recognition of a distance by recollective thought, or by means of a sensory process which is under the influence of set and of prior experience.
Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.
Diseases affecting the eye.
The time from the onset of a stimulus until a response is observed.
A genus, commonly called budgerigars, in the family PSITTACIDAE. In the United States they are considered one of the five species of PARAKEETS.
Presence of an intraocular lens after cataract extraction.
Visualization of a vascular system after intravenous injection of a fluorescein solution. The images may be photographed or televised. It is used especially in studying the retinal and uveal vasculature.
Agents causing contraction of the pupil of the eye. Some sources use the term miotics only for the parasympathomimetics but any drug used to induce miosis is included here.
A procedure to surgically correct REFRACTIVE ERRORS by cutting radial slits into the CORNEA to change its refractive properties.
A syndrome characterized by marked limitation of abduction of the eye, variable limitation of adduction and retraction of the globe, and narrowing of the palpebral fissure on attempted adduction. The condition is caused by aberrant innervation of the lateral rectus by fibers of the OCULOMOTOR NERVE.
Hereditary, progressive degeneration of the neuroepithelium of the retina characterized by night blindness and progressive contraction of the visual field.
Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.
An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum.
Assessment of psychological variables by the application of mathematical procedures.
A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.
The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.
A form of ocular misalignment characterized by an excessive convergence of the visual axes, resulting in a "cross-eye" appearance. An example of this condition occurs when paralysis of the lateral rectus muscle causes an abnormal inward deviation of one eye on attempted gaze.
A condition in which the intraocular pressure is elevated above normal and which may lead to glaucoma.
Signals for an action; that specific portion of a perceptual field or pattern of stimuli to which a subject has learned to respond.
An imaging method using LASERS that is used for mapping subsurface structure. When a reflective site in the sample is at the same optical path length (coherence) as the reference mirror, the detector observes interference fringes.
Performance of an act one or more times, with a view to its fixation or improvement; any performance of an act or behavior that leads to learning.
A noninflammatory, usually bilateral protrusion of the cornea, the apex being displaced downward and nasally. It occurs most commonly in females at about puberty. The cause is unknown but hereditary factors may play a role. The -conus refers to the cone shape of the corneal protrusion. (From Dorland, 27th ed)
An analogue of GAMMA-AMINOBUTYRIC ACID. It is an irreversible inhibitor of 4-AMINOBUTYRATE TRANSAMINASE, the enzyme responsible for the catabolism of GAMMA-AMINOBUTYRIC ACID. (From Martindale The Extra Pharmacopoeia, 31st ed)
An oval area in the retina, 3 to 5 mm in diameter, usually located temporal to the posterior pole of the eye and slightly below the level of the optic disk. It is characterized by the presence of a yellow pigment diffusely permeating the inner layers, contains the fovea centralis in its center, and provides the best phototropic visual acuity. It is devoid of retinal blood vessels, except in its periphery, and receives nourishment from the choriocapillaris of the choroid. (From Cline et al., Dictionary of Visual Science, 4th ed)
The pressure of the fluids in the eye.
The functional superiority and preferential use of one eye over the other. The term is usually applied to superiority in sighting (VISUAL PERCEPTION) or motor task but not difference in VISUAL ACUITY or dysfunction of one of the eyes. Ocular dominance can be modified by visual input and NEUROTROPHIC FACTORS.
A refractive error in which rays of light entering the eye parallel to the optic axis are brought to a focus behind the retina, as a result of the eyeball being too short from front to back. It is also called farsightedness because the near point is more distant than it is in emmetropia with an equal amplitude of accommodation. (Dorland, 27th ed)
## I'm sorry for any confusion, but "Alabama" is not a medical term or concept. It is a geographical location, referring to the 22nd state admitted to the United States of America, located in the southeastern region. If you have any questions related to healthcare, medicine, or health conditions, I'd be happy to help with those!
The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.
Voluntary or reflex-controlled movements of the eye.
Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.
Fluid accumulation in the outer layer of the MACULA LUTEA that results from intraocular or systemic insults. It may develop in a diffuse pattern where the macula appears thickened or it may acquire the characteristic petaloid appearance referred to as cystoid macular edema. Although macular edema may be associated with various underlying conditions, it is most commonly seen following intraocular surgery, venous occlusive disease, DIABETIC RETINOPATHY, and posterior segment inflammatory disease. (From Survey of Ophthalmology 2004; 49(5) 470-90)
The 2nd cranial nerve which conveys visual information from the RETINA to the brain. The nerve carries the axons of the RETINAL GANGLION CELLS which sort at the OPTIC CHIASM and continue via the OPTIC TRACTS to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the SUPERIOR COLLICULI and the SUPRACHIASMATIC NUCLEI. Though known as the second cranial nerve, it is considered part of the CENTRAL NERVOUS SYSTEM.
The continuous sequential physiological and psychological maturing of an individual from birth up to but not including ADOLESCENCE.
A transparent, biconvex structure of the EYE, enclosed in a capsule and situated behind the IRIS and in front of the vitreous humor (VITREOUS BODY). It is slightly overlapped at its margin by the ciliary processes. Adaptation by the CILIARY BODY is crucial for OCULAR ACCOMMODATION.
The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous CORNEAL EPITHELIUM; BOWMAN MEMBRANE; CORNEAL STROMA; DESCEMET MEMBRANE; and mesenchymal CORNEAL ENDOTHELIUM. It serves as the first refracting medium of the eye. It is structurally continuous with the SCLERA, avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the TRIGEMINAL NERVE via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed)
Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.
The blood vessels which supply and drain the RETINA.
Methods and procedures for the diagnosis of diseases of the eye or of vision disorders.
A genus of the subfamily CERCOPITHECINAE, family CERCOPITHECIDAE, consisting of 16 species inhabiting forests of Africa, Asia, and the islands of Borneo, Philippines, and Celebes.
Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
Psychophysical technique that permits the estimation of the bias of the observer as well as detectability of the signal (i.e., stimulus) in any sensory modality. (From APA, Thesaurus of Psychological Index Terms, 8th ed.)
A species of the genus MACACA inhabiting India, China, and other parts of Asia. The species is used extensively in biomedical research and adapts very well to living with humans.
Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.
The use of green light-producing LASERS to stop bleeding. The green light is selectively absorbed by HEMOGLOBIN, thus triggering BLOOD COAGULATION.
A pathological process consisting of the formation of new blood vessels in the CHOROID.
The diversion of RADIATION (thermal, electromagnetic, or nuclear) from its original path as a result of interactions or collisions with atoms, molecules, or larger particles in the atmosphere or other media. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
The coordination of a sensory or ideational (cognitive) process and a motor activity.
Application of computer programs designed to assist the physician in solving a diagnostic problem.
Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.
Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.
The period following a surgical operation.

Why and how is soft copy reading possible in clinical practice? (1/2967)

The properties of the human visual system (HVS) relevant to the diagnostic process are described after a brief introduction on the general problems and advantages of using soft copy for primary radiology interpretations. At various spatial and temporal frequencies the contrast sensitivity defines the spatial resolution of the eye-brain system and the sensitivity to flicker. The adaptation to the displayed radiological scene and the ambient illumination determine the dynamic range for the operation of the HVS. Although image display devices are determined mainly by state-of-the-art technology, analysis of the HVS may suggest technical characteristics for electronic displays that will help to optimize the display to the operation of the HVS. These include display size, spatial resolution, contrast resolution, luminance range, and noise, from which further consequences for the technical components of a monitor follow. It is emphasized that routine monitor quality control must be available in clinical practice. These image quality measures must be simple enough to be applied as part of the daily routine. These test instructions might also serve as elements of technical acceptance and constancy tests.  (+info)

Impairment in preattentive visual processing in patients with Parkinson's disease. (2/2967)

We explored the possibility of whether preattentive visual processing is impaired in Parkinson's disease. With this aim, visual discrimination thresholds for orientation texture stimuli were determined in two separate measurement sessions in 16 patients with idiopathic Parkinson's disease. The results were compared with those of 16 control subjects age-matched and 16 young healthy volunteers. Discrimination thresholds were measured in a four-alternative spatial forced-choice paradigm, in which subjects judged the location of a target embedded in a background of distractors. Four different stimulus configurations were employed: (i) a group of vertical targets among horizontal distractors ('vertical line targets'); (ii) targets with varying levels of orientation difference on a background of spatially filtered vertically oriented noise ('Gaussian filtered noise'); (iii) one 'L' among 43 '+' signs ('texton'), all of which assess preattentive visual processing; and (iv) control condition, of one 'L' among 43 'T' distractors ('non-texton' search target), which reflects attentive visual processing. In two of the preattentive tasks (filtered noise and texton), patients with Parkinson's disease required significantly greater orientation differences and longer stimulus durations, respectively. In contrast, their performance in the vertical line target and non-texton search target was comparable to that of the matched control subjects. These differences were more pronounced in the first compared with the second session. Duration of illness and age within the patient group correlated significantly with test performance. In all conditions tested, the young control subjects performed significantly better than the more elderly control group, further indicating an effect of age on this form of visual processing. The results suggest that, in addition to the well documented impairment in retinal processing, idiopathic Parkinson's disease is associated with a deficit in preattentive cortical visual processing.  (+info)

Accurate memory for colour but not pattern contrast in chicks. (3/2967)

The visual displays of animals and plants often look dramatic and colourful to us, but what information do they convey to their intended, non-human, audience [1] [2]? One possibility is that stimulus values are judged accurately - so, for example, a female might choose a suitor if he displays a specific colour [3]. Alternatively, as for human advertising, displays may attract attention without giving information, perhaps by exploiting innate preferences for bright colours or symmetry [2] [4] [5]. To address this issue experimentally, we investigated chicks' memories of visual patterns. Food was placed in patterned paper containers which, like seed pods or insect prey, must be manipulated to extract food and their patterns learnt. To establish what was learnt, birds were tested on familiar stimuli and on alternative stimuli of differing colour or contrast. For colour, birds selected the trained stimulus; for contrast, they preferred high contrast patterns over the familiar. These differing responses to colour and contrast show how separate components of display patterns could serve different roles, with colour being judged accurately whereas pattern contrast attracts attention.  (+info)

Characteristics of discrepancies between self-reported visual function and measured reading speed. Salisbury Eye Evaluation Project Team. (4/2967)

PURPOSE: Visual impairment is a risk factor for morbidity in the elderly and is often screened for by self-report. This study evaluates whether there are subsets for whom there is a discrepancy between self-reported and measured function. METHODS: The prevalence of a discrepancy between self-reported difficulty reading a newspaper and measured reading speed was determined in 2520 community-based men and women, aged 65 to 84 years, and the discrepant group characterized by polychotomous regression. RESULTS: Of subjects who reported minimal difficulty reading a newspaper, 10.8% (227/2107) read newsprint-sized text (0.21 degrees) more slowly than 80 words/min, a level previously shown to be necessary for sustained reading. Poor visual acuity, presence of psychiatric symptoms, and less satisfaction with vision were associated with being in the group that read slowly and reported difficulty with reading. Better cognition, better visual acuity, more years of education, white race, and fewer psychiatric symptoms were associated with being in the group that read more quickly and reported minimal difficulty. When reading the text size at which subjects read their fastest, only 2.6% of those with minimal difficulty remained discrepant. These individuals were more likely to have less education, be male, be African American, and have poorer cognitive status than those who did not remain discrepant. CONCLUSIONS: A subset of the elderly population have a substantial discrepancy between self-reported reading difficulty and measured reading speed. In some, this discrepancy may be based on underlying expectations and experiences, and in others it may represent a transition from no visual impairment to visual impairment.  (+info)

Perceived visual ability for independent mobility in persons with retinitis pigmentosa. (5/2967)

PURPOSE: To determine the distribution of perceived ability for independent mobility in people who are at various stages of retinitis pigmentosa (RP). METHODS: A questionnaire was developed to ask subjects to rate how difficult they found each of 35 mobility situations if they had no assistance. The scale was 1 (no difficulty) to 5 (extreme difficulty). In each of 127 subjects, the Rasch analysis, a latent trait analysis, was used to convert the ordinal difficulty ratings into interval measures of perceived visual ability for independent mobility. RESULTS: Content validity of the questionnaire was shown by good separation indexes (4.55 and 8.0) and high reliability scores (0.96 and 0.98) for the person and the item parameters. Construct validity was shown with model fit statistics. Criterion validity of the questionnaire was shown by good discrimination among mobility-related behavior such as "limit independent travel," "always ask for accompaniment," "use a mobility aid," and "have a fear of falling." The mobility situation shown to require the least visual ability was "moving about in the home"; the situation requiring the most was "walking at night." Bivariate regression analysis determined that for every decade of disease progression, perceived visual ability for mobility decreased by approximately 0.5 logit, which was slightly less than 10% of the total range in the study sample. A linear combination of the visual function measures, log minimum angle of resolution, log contrast sensitivity, and log retinal area accounted for 57% of the variability in the person measure. CONCLUSIONS: The patient-based assessment, developed to determine difficulty across a range of mobility situations, is a valid way to measure perceived ability for independent mobility. This latent trait varies systematically with the progression of RP and with visual function measures.  (+info)

Cone signal contributions to electroretinograms [correction of electrograms] in dichromats and trichromats. (6/2967)

PURPOSE: To find out how the different cone types contribute to the electroretinogram (ERG) by quantifying the contribution of the signal pathways originating in the long (L-) and the middle (M-) wavelength-sensitive cones to the total ERG response amplitude and phase. METHODS: ERG response amplitudes and phases were measured to cone-isolating stimuli and to different combinations of L- and M-cone modulation. Conditions were chosen to exclude any contribution of the short wavelength-sensitive (S-) cones. The sensitivity of the ERG to the L and the M cones was defined as the cone contrast gain. RESULTS: In the present paper, a model is provided that describes the ERG contrast gains and ERG thresholds in dichromats and color normal trichromats. For the X-chromosome-linked dichromats, the contrast gains of only one cone type (either the L or the M cones) sufficed to describe the ERG thresholds for all stimulus conditions. Data suggest that the M-cone contrast gains of protanopes are larger than the L-cone contrast gains of deuteranopes. The response thresholds of the trichromats are modeled by assuming a vector summation of signals originating in the L and the M cones. Their L- and M-cone contrast gains are close to a linear interpolation of the data obtained from the dichromats. Nearly all trichromats had larger L- than M-cone contrast gains. Data from a large population of trichromats were examined to study the individual variations in cone weightings and in the phases of the cone pathway responses. CONCLUSIONS: The data strongly suggest that the missing cone type in dichromats is replaced by the remaining cone type. The mean L-cone to M-cone weighting ratio in trichromats was found to be approximately 4:1. But there is a substantial interindividual variability between trichromats. The response phases of the L- and the M-cone pathways can be reliably quantified using the response phases to the cone-isolating stimuli or using a vector addition of L- and M-cone signals.  (+info)

Selective color constancy deficits after circumscribed unilateral brain lesions. (7/2967)

The color of an object, when part of a complex scene, is determined not only by its spectral reflectance but also by the colors of all other objects in the scene (von Helmholtz, 1886; Ives, 1912; Land, 1959). By taking global color information into account, the visual system is able to maintain constancy of the color appearance of the object, despite large variations in the light incident on the retina arising from changes in the spectral content of the illuminating light (Hurlbert, 1998; Maloney, 1999). The neural basis of this color constancy is, however, poorly understood. Although there seems to be a prominent role for retinal, cone-specific adaptation mechanisms (von Kries, 1902; Poppel, 1986; Foster and Nascimento, 1994), the contribution of cortical mechanisms to color constancy is still unclear (Land et al., 1983; D'Zmura and Lennie, 1986). We examined the color perception of 27 patients with defined unilateral lesions mainly located in the parieto-temporo-occipital and fronto-parieto-temporal cortex. With a battery of clinical and specially designed color vision tests we tried to detect and differentiate between possible deficits in central color processing. Our results show that color constancy can be selectively impaired after circumscribed unilateral lesions in parieto-temporal cortex of the left or right hemisphere. Five of 27 patients exhibited significant deficits in a color constancy task, but all of the 5 performed well in color discrimination or higher-level visual tasks, such as the association of colors with familiar objects. These results indicate that the computations underlying color constancy are mediated by specialized cortical circuitry, which is independent of the neural substrate for color discrimination and for assigning colors to objects.  (+info)

Geometric representation of the mechanisms underlying human curvature detection. (8/2967)

Combined manipulation of blur, line length and contrast reveal two distinct processes involved in curvature detection. When line length is small relative to blur, thresholds are almost directly proportional to blur and independent of line length. When line length is large relative to blur thresholds are directly proportional to line length and independent of blur. The aspect ratio (line length/blur) of curved contours represents a scale-invariant metric which forms the decisive factor in determining curvature performance.  (+info)

Contrast sensitivity is a measure of the ability to distinguish between an object and its background based on differences in contrast, rather than differences in luminance. Contrast refers to the difference in light intensity between an object and its immediate surroundings. Contrast sensitivity is typically measured using specially designed charts that have patterns of parallel lines with varying widths and contrast levels.

In clinical settings, contrast sensitivity is often assessed as part of a comprehensive visual examination. Poor contrast sensitivity can affect a person's ability to perform tasks such as reading, driving, or distinguishing objects from their background, especially in low-light conditions. Reduced contrast sensitivity is a common symptom of various eye conditions, including cataracts, glaucoma, and age-related macular degeneration.

Visual acuity is a measure of the sharpness or clarity of vision. It is usually tested by reading an eye chart from a specific distance, such as 20 feet (6 meters). The standard eye chart used for this purpose is called the Snellen chart, which contains rows of letters that decrease in size as you read down the chart.

Visual acuity is typically expressed as a fraction, with the numerator representing the testing distance and the denominator indicating the smallest line of type that can be read clearly. For example, if a person can read the line on the eye chart that corresponds to a visual acuity of 20/20, it means they have normal vision at 20 feet. If their visual acuity is 20/40, it means they must be as close as 20 feet to see what someone with normal vision can see at 40 feet.

It's important to note that visual acuity is just one aspect of overall vision and does not necessarily reflect other important factors such as peripheral vision, depth perception, color vision, or contrast sensitivity.

Vision tests are a series of procedures used to assess various aspects of the visual system, including visual acuity, accommodation, convergence, divergence, stereopsis, color vision, and peripheral vision. These tests help healthcare professionals diagnose and manage vision disorders, such as nearsightedness, farsightedness, astigmatism, amblyopia, strabismus, and eye diseases like glaucoma, cataracts, and macular degeneration. Common vision tests include:

1. Visual acuity test (Snellen chart or letter chart): Measures the sharpness of a person's vision at different distances.
2. Refraction test: Determines the correct lens prescription for glasses or contact lenses by assessing how light is bent as it passes through the eye.
3. Color vision test: Evaluates the ability to distinguish between different colors and color combinations, often using pseudoisochromatic plates or Ishihara tests.
4. Stereopsis test: Assesses depth perception and binocular vision by presenting separate images to each eye that, when combined, create a three-dimensional effect.
5. Cover test: Examines eye alignment and the presence of strabismus (crossed eyes or turned eyes) by covering and uncovering each eye while observing eye movements.
6. Ocular motility test: Assesses the ability to move the eyes in various directions and coordinate both eyes during tracking and convergence/divergence movements.
7. Accommodation test: Evaluates the ability to focus on objects at different distances by using lenses, prisms, or dynamic retinoscopy.
8. Pupillary response test: Examines the size and reaction of the pupils to light and near objects.
9. Visual field test: Measures the peripheral (side) vision using automated perimetry or manual confrontation techniques.
10. Slit-lamp examination: Inspects the structures of the front part of the eye, such as the cornea, iris, lens, and anterior chamber, using a specialized microscope.

These tests are typically performed by optometrists, ophthalmologists, or other vision care professionals during routine eye examinations or when visual symptoms are present.

In the context of ophthalmology and optometry, glare refers to a visual sensation caused by excessive brightness or contrast that interferes with the ability to see comfortably or clearly. It can be caused by direct or reflected light sources that enter the eye and scatter within the eye or on the surface of the eye, reducing contrast and visibility. Glare can lead to discomfort, disability, or both, and it can significantly impact visual performance in various activities such as driving, reading, and using digital devices. There are different types of glare, including direct glare, reflected glare, and veiling glare, each with its own characteristics and effects on vision.

Sensory thresholds are the minimum levels of stimulation that are required to produce a sensation in an individual, as determined through psychophysical testing. These tests measure the point at which a person can just barely detect the presence of a stimulus, such as a sound, light, touch, or smell.

There are two types of sensory thresholds: absolute and difference. Absolute threshold is the minimum level of intensity required to detect a stimulus 50% of the time. Difference threshold, also known as just noticeable difference (JND), is the smallest change in intensity that can be detected between two stimuli.

Sensory thresholds can vary between individuals and are influenced by factors such as age, attention, motivation, and expectations. They are often used in clinical settings to assess sensory function and diagnose conditions such as hearing or vision loss.

Amblyopia is a medical condition that affects the visual system, specifically the way the brain and eyes work together. It is often referred to as "lazy eye" and is characterized by reduced vision in one or both eyes that is not correctable with glasses or contact lenses alone. This occurs because the brain favors one eye over the other, causing the weaker eye to become neglected and underdeveloped.

Amblyopia can result from various conditions such as strabismus (eye misalignment), anisometropia (significant difference in prescription between the two eyes), or deprivation (such as a cataract that blocks light from entering the eye). Treatment for amblyopia typically involves correcting any underlying refractive errors, patching or blurring the stronger eye to force the weaker eye to work, and/or vision therapy. Early intervention is crucial to achieve optimal visual outcomes.

Vision disorders refer to a wide range of conditions that affect the visual system and result in various symptoms, such as blurry vision, double vision, distorted vision, impaired depth perception, and difficulty with visual tracking or focusing. These disorders can be categorized into several types, including:

1. Refractive errors: These occur when the shape of the eye prevents light from focusing directly on the retina, resulting in blurry vision. Examples include myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia (age-related loss of near vision).
2. Strabismus: Also known as crossed eyes or walleye, strabismus is a misalignment of the eyes where they point in different directions, which can lead to double vision or loss of depth perception.
3. Amblyopia: Often called lazy eye, amblyopia is a condition where one eye has reduced vision due to lack of proper visual development during childhood. It may be caused by strabismus, refractive errors, or other factors that interfere with normal visual development.
4. Accommodative disorders: These involve problems with the focusing ability of the eyes, such as convergence insufficiency (difficulty focusing on close objects) and accommodative dysfunction (inability to maintain clear vision at different distances).
5. Binocular vision disorders: These affect how the eyes work together as a team, leading to issues like poor depth perception, eye strain, and headaches. Examples include convergence insufficiency, divergence excess, and suppression.
6. Ocular motility disorders: These involve problems with eye movement, such as nystagmus (involuntary eye movements), strabismus, or restricted extraocular muscle function.
7. Visual processing disorders: These affect the brain's ability to interpret and make sense of visual information, even when the eyes themselves are healthy. Symptoms may include difficulty with reading, recognizing shapes and objects, and understanding spatial relationships.
8. Low vision: This term refers to significant visual impairment that cannot be fully corrected with glasses, contact lenses, medication, or surgery. It includes conditions like macular degeneration, diabetic retinopathy, glaucoma, and cataracts.
9. Blindness: Complete loss of sight in both eyes, which can be caused by various factors such as injury, disease, or genetic conditions.

Psychophysics is not a medical term per se, but rather a subfield of psychology and neuroscience that studies the relationship between physical stimuli and the sensations and perceptions they produce. It involves the quantitative investigation of psychological functions, such as how brightness or loudness is perceived relative to the physical intensity of light or sound.

In medical contexts, psychophysical methods may be used in research or clinical settings to understand how patients with neurological conditions or sensory impairments perceive and respond to different stimuli. This information can inform diagnostic assessments, treatment planning, and rehabilitation strategies.

Night vision refers to the ability to see in low light conditions, typically during night time. In a medical context, it often relates to the functionality of the eye and visual system. There are two types of night vision:

1. Scotopic vision: This is the primary type of night vision, enabled by the rod cells in our retina which are highly sensitive to light but lack color vision. During twilight or night conditions, when light levels are low, the rods take over from the cone cells (which are responsible for color and daytime vision) and provide us with limited vision, typically in shades of gray.

2. Mesopic vision: This is a state between photopic (daytime) and scotopic (night-time) vision, where both rod and cone cells contribute to vision. It allows for better color discrimination and visual acuity compared to scotopic vision alone.

In some cases, night vision can be impaired due to eye conditions such as cataracts, glaucoma, or retinal disorders. There are also medical devices called night vision goggles that amplify available light to enhance a person's ability to see in low-light environments.

Sensitivity and specificity are statistical measures used to describe the performance of a diagnostic test or screening tool in identifying true positive and true negative results.

* Sensitivity refers to the proportion of people who have a particular condition (true positives) who are correctly identified by the test. It is also known as the "true positive rate" or "recall." A highly sensitive test will identify most or all of the people with the condition, but may also produce more false positives.
* Specificity refers to the proportion of people who do not have a particular condition (true negatives) who are correctly identified by the test. It is also known as the "true negative rate." A highly specific test will identify most or all of the people without the condition, but may also produce more false negatives.

In medical testing, both sensitivity and specificity are important considerations when evaluating a diagnostic test. High sensitivity is desirable for screening tests that aim to identify as many cases of a condition as possible, while high specificity is desirable for confirmatory tests that aim to rule out the condition in people who do not have it.

It's worth noting that sensitivity and specificity are often influenced by factors such as the prevalence of the condition in the population being tested, the threshold used to define a positive result, and the reliability and validity of the test itself. Therefore, it's important to consider these factors when interpreting the results of a diagnostic test.

Ocular vision refers to the ability to process and interpret visual information that is received by the eyes. This includes the ability to see clearly and make sense of the shapes, colors, and movements of objects in the environment. The ocular system, which includes the eye and related structures such as the optic nerve and visual cortex of the brain, works together to enable vision.

There are several components of ocular vision, including:

* Visual acuity: the clarity or sharpness of vision
* Field of vision: the extent of the visual world that is visible at any given moment
* Color vision: the ability to distinguish different colors
* Depth perception: the ability to judge the distance of objects in three-dimensional space
* Contrast sensitivity: the ability to distinguish an object from its background based on differences in contrast

Disorders of ocular vision can include refractive errors such as nearsightedness or farsightedness, as well as more serious conditions such as cataracts, glaucoma, and macular degeneration. These conditions can affect one or more aspects of ocular vision and may require medical treatment to prevent further vision loss.

Color perception refers to the ability to detect, recognize, and differentiate various colors and color patterns in the visual field. This complex process involves the functioning of both the eyes and the brain.

The eye's retina contains two types of photoreceptor cells called rods and cones. Rods are more sensitive to light and dark changes and help us see in low-light conditions, but they do not contribute much to color vision. Cones, on the other hand, are responsible for color perception and function best in well-lit conditions.

There are three types of cone cells, each sensitive to a particular range of wavelengths corresponding to blue, green, and red colors. The combination of signals from these three types of cones allows us to perceive a wide spectrum of colors.

The brain then interprets these signals and translates them into the perception of different colors and hues. It is important to note that color perception can be influenced by various factors, including cultural background, personal experiences, and even language. Some individuals may also have deficiencies in color perception due to genetic or acquired conditions, such as color blindness or cataracts.

Photic stimulation is a medical term that refers to the exposure of the eyes to light, specifically repetitive pulses of light, which is used as a method in various research and clinical settings. In neuroscience, it's often used in studies related to vision, circadian rhythms, and brain function.

In a clinical context, photic stimulation is sometimes used in the diagnosis of certain medical conditions such as seizure disorders (like epilepsy). By observing the response of the brain to this light stimulus, doctors can gain valuable insights into the functioning of the brain and the presence of any neurological disorders.

However, it's important to note that photic stimulation should be conducted under the supervision of a trained healthcare professional, as improper use can potentially trigger seizures in individuals who are susceptible to them.

Color vision defects, also known as color blindness, are conditions in which a person has difficulty distinguishing between certain colors. The most common types of color vision defects involve the inability to distinguish between red and green or blue and yellow. These deficiencies result from an alteration or absence of one or more of the three types of cone cells in the retina that are responsible for normal color vision.

In red-green color vision defects, there is a problem with either the red or green cones, or both. This results in difficulty distinguishing between these two colors and their shades. Protanopia is a type of red-green color vision defect where there is an absence of red cone cells, making it difficult to distinguish between red and green as well as between red and black or green and black. Deuteranopia is another type of red-green color vision defect where there is an absence of green cone cells, resulting in similar difficulties distinguishing between red and green, as well as between blue and yellow.

Blue-yellow color vision defects are less common than red-green color vision defects. Tritanopia is a type of blue-yellow color vision defect where there is an absence of blue cone cells, making it difficult to distinguish between blue and yellow, as well as between blue and purple or yellow and pink.

Color vision defects are usually inherited and present from birth, but they can also result from eye diseases, chemical exposure, aging, or medication side effects. They affect both men and women, although red-green color vision defects are more common in men than in women. People with color vision defects may have difficulty with tasks that require color discrimination, such as matching clothes, selecting ripe fruit, reading colored maps, or identifying warning signals. However, most people with mild to moderate color vision defects can adapt and function well in daily life.

Visual fields refer to the total area in which objects can be seen while keeping the eyes focused on a central point. It is the entire area that can be observed using peripheral (side) vision while the eye gazes at a fixed point. A visual field test is used to detect blind spots or gaps (scotomas) in a person's vision, which could indicate various medical conditions such as glaucoma, retinal damage, optic nerve disease, brain tumors, or strokes. The test measures both the central and peripheral vision and maps the entire area that can be seen when focusing on a single point.

Visual pattern recognition is the ability to identify and interpret patterns in visual information. In a medical context, it often refers to the process by which healthcare professionals recognize and diagnose medical conditions based on visible signs or symptoms. This can involve recognizing the characteristic appearance of a rash, wound, or other physical feature associated with a particular disease or condition. It may also involve recognizing patterns in medical images such as X-rays, CT scans, or MRIs.

In the field of radiology, for example, visual pattern recognition is a critical skill. Radiologists are trained to recognize the typical appearances of various diseases and conditions in medical images. This allows them to make accurate diagnoses based on the patterns they see. Similarly, dermatologists use visual pattern recognition to identify skin abnormalities and diseases based on the appearance of rashes, lesions, or other skin changes.

Overall, visual pattern recognition is an essential skill in many areas of medicine, allowing healthcare professionals to quickly and accurately diagnose medical conditions based on visible signs and symptoms.

Space perception, in the context of neuroscience and psychology, refers to the ability to perceive and understand the spatial arrangement of objects and their relationship to oneself. It involves integrating various sensory inputs such as visual, auditory, tactile, and proprioceptive information to create a coherent three-dimensional representation of our environment.

This cognitive process enables us to judge distances, sizes, shapes, and movements of objects around us. It also helps us navigate through space, reach for objects, avoid obstacles, and maintain balance. Disorders in space perception can lead to difficulties in performing everyday activities and may be associated with neurological conditions such as stroke, brain injury, or neurodevelopmental disorders like autism.

Flicker Fusion is the frequency at which an intermittent light stimulus appears to be completely steady or continuous to the average human observer. In other words, it is the rate at which a flickering light source transitions from being perceived as distinct flashes to a smooth and constant emission of light. The exact threshold can vary depending on factors such as the intensity of the light, its size, and the observer's visual acuity.

Flicker Fusion has important implications in various fields, including visual perception research, display technology, and neurology. In clinical settings, assessing a patient's flicker fusion threshold can help diagnose or monitor conditions affecting the nervous system, such as multiple sclerosis or migraines.

Visual pathways, also known as the visual system or the optic pathway, refer to the series of specialized neurons in the nervous system that transmit visual information from the eyes to the brain. This complex network includes the retina, optic nerve, optic chiasma, optic tract, lateral geniculate nucleus, pulvinar, and the primary and secondary visual cortices located in the occipital lobe of the brain.

The process begins when light enters the eye and strikes the photoreceptor cells (rods and cones) in the retina, converting the light energy into electrical signals. These signals are then transmitted to bipolar cells and subsequently to ganglion cells, whose axons form the optic nerve. The fibers from each eye's nasal hemiretina cross at the optic chiasma, while those from the temporal hemiretina continue without crossing. This results in the formation of the optic tract, which carries visual information from both eyes to the opposite side of the brain.

The majority of fibers in the optic tract synapse with neurons in the lateral geniculate nucleus (LGN), a part of the thalamus. The LGN sends this information to the primary visual cortex, also known as V1 or Brodmann area 17, located in the occipital lobe. Here, simple features like lines and edges are initially processed. Further processing occurs in secondary (V2) and tertiary (V3-V5) visual cortices, where more complex features such as shape, motion, and depth are analyzed. Ultimately, this information is integrated to form our perception of the visual world.

Evoked potentials, visual, also known as visually evoked potentials (VEPs), are electrical responses recorded from the brain following the presentation of a visual stimulus. These responses are typically measured using electroencephalography (EEG) and can provide information about the functioning of the visual pathways in the brain.

There are several types of VEPs, including pattern-reversal VEPs and flash VEPs. Pattern-reversal VEPs are elicited by presenting alternating checkerboard patterns, while flash VEPs are elicited by flashing a light. The responses are typically analyzed in terms of their latency (the time it takes for the response to occur) and amplitude (the size of the response).

VEPs are often used in clinical settings to help diagnose and monitor conditions that affect the visual system, such as multiple sclerosis, optic neuritis, and brainstem tumors. They can also be used in research to study the neural mechanisms underlying visual perception.

Form perception, also known as shape perception, is not a term that has a specific medical definition. However, in the field of neuropsychology and sensory perception, form perception refers to the ability to recognize and interpret different shapes and forms of objects through visual processing. This ability is largely dependent on the integrity of the visual cortex and its ability to process and interpret information received from the retina.

Damage to certain areas of the brain, particularly in the occipital and parietal lobes, can result in deficits in form perception, leading to difficulties in recognizing and identifying objects based on their shape or form. This condition is known as visual agnosia and can be a symptom of various neurological disorders such as stroke, brain injury, or degenerative diseases like Alzheimer's disease.

The fovea centralis, also known as the macula lutea, is a small pit or depression located in the center of the retina, an light-sensitive tissue at the back of the eye. It is responsible for sharp, detailed vision (central vision) and color perception. The fovea contains only cones, the photoreceptor cells that are responsible for color vision and high visual acuity. It has a higher concentration of cones than any other area in the retina, allowing it to provide the greatest detail and color discrimination. The center of the fovea is called the foveola, which contains the highest density of cones and is avascular, meaning it lacks blood vessels to avoid interfering with the light passing through to the photoreceptor cells.

Orthoptics is a specialty within the field of ophthalmology that deals with the diagnosis and treatment of visual system disorders, particularly those related to eye movements and alignment. It involves the use of various techniques such as eye exercises, glasses, prisms, and surgery to correct issues like strabismus (crossed eyes), amblyopia (lazy eye), and diplopia (double vision). Orthoptists are healthcare professionals who have received specialized training in this area.

Ocular adaptation is the ability of the eye to adjust and accommodate to changes in visual input and lighting conditions. This process allows the eye to maintain a clear and focused image over a range of different environments and light levels. There are several types of ocular adaptation, including:

1. Light Adaptation: This refers to the eye's ability to adjust to different levels of illumination. When moving from a dark environment to a bright one, the pupils constrict to let in less light, and the sensitivity of the retina decreases. Conversely, when moving from a bright environment to a dark one, the pupils dilate to let in more light, and the sensitivity of the retina increases.
2. Dark Adaptation: This is the process by which the eye adjusts to low light conditions. It involves the dilation of the pupils and an increase in the sensitivity of the rods (specialised cells in the retina that are responsible for vision in low light conditions). Dark adaptation can take several minutes to occur fully.
3. Color Adaptation: This refers to the eye's ability to adjust to changes in the color temperature of light sources. For example, when moving from a room lit by incandescent light to one lit by fluorescent light, the eye may need to adjust its perception of colors to maintain accurate color vision.
4. Accommodation: This is the process by which the eye changes focus from distant to near objects. The lens of the eye changes shape to bend the light rays entering the eye and bring them into sharp focus on the retina.

Overall, ocular adaptation is an essential function that allows us to see clearly and accurately in a wide range of environments and lighting conditions.

A pupil, in medical terms, refers to the circular opening in the center of the iris (the colored part of the eye) that allows light to enter and reach the retina. The size of the pupil can change involuntarily in response to light intensity and emotional state, as well as voluntarily through certain eye exercises or with the use of eye drops. Pupillary reactions are important in clinical examinations as they can provide valuable information about the nervous system's functioning, particularly the brainstem and cranial nerves II and III.

Binocular vision refers to the ability to use both eyes together to create a single, three-dimensional image of our surroundings. This is achieved through a process called binocular fusion, where the images from each eye are aligned and combined in the brain to form a unified perception.

The term "binocular vision" specifically refers to the way that our visual system integrates information from both eyes to create depth perception and enhance visual clarity. When we view an object with both eyes, they focus on the same point in space and send slightly different images to the brain due to their slightly different positions. The brain then combines these images to create a single, three-dimensional image that allows us to perceive depth and distance.

Binocular vision is important for many everyday activities, such as driving, reading, and playing sports. Disorders of binocular vision can lead to symptoms such as double vision, eye strain, and difficulty with depth perception.

Color perception tests are a type of examination used to evaluate an individual's ability to perceive and distinguish different colors. These tests typically consist of a series of plates or images that contain various patterns or shapes displayed in different colors. The person being tested is then asked to identify or match the colors based on specific instructions.

There are several types of color perception tests, including:

1. Ishihara Test: This is a commonly used test for red-green color deficiency. It consists of a series of plates with circles made up of dots in different sizes and colors. Within these circles, there may be a number or symbol visible only to those with normal color vision or to those with specific types of color blindness.
2. Farnsworth D-15 Test: This test measures an individual's ability to arrange colored caps in a specific order based on their hue. It is often used to diagnose and monitor the progression of color vision deficiencies.
3. Hardy-Rand-Rittler (HRR) Test: This is another type of color arrangement test that measures an individual's ability to distinguish between different colors based on their hue, saturation, and brightness.
4. Color Discrimination Tests: These tests measure an individual's ability to distinguish between two similar colors that are presented side by side or in close proximity.
5. Anomaloscope Test: This is a more sophisticated test that measures the degree of color vision deficiency by asking the person to match the brightness and hue of two lights.

Color perception tests are often used in occupational settings, such as aviation, military, and manufacturing, where color discrimination is critical for safety and performance. They may also be used in educational and clinical settings to diagnose and monitor color vision deficiencies.

Myopia, also known as nearsightedness, is a common refractive error of the eye. It occurs when the eye is either too long or the cornea (the clear front part of the eye) is too curved. As a result, light rays focus in front of the retina instead of directly on it, causing distant objects to appear blurry while close objects remain clear.

Myopia typically develops during childhood and can progress gradually or rapidly until early adulthood. It can be corrected with glasses, contact lenses, or refractive surgery such as LASIK. Regular eye examinations are essential for people with myopia to monitor any changes in their prescription and ensure proper correction.

While myopia is generally not a serious condition, high levels of nearsightedness can increase the risk of certain eye diseases, including cataracts, glaucoma, retinal detachment, and myopic degeneration. Therefore, it's crucial to manage myopia effectively and maintain regular follow-ups with an eye care professional.

Color vision is the ability to perceive and differentiate colors, which is a result of the way that our eyes and brain process different wavelengths of light. In the eye, there are two types of photoreceptor cells called rods and cones. While rods are more sensitive to low levels of light and help us see in dim conditions, cones are responsible for color vision.

There are three types of cone cells in the human eye, each containing a different type of pigment that is sensitive to specific wavelengths of light. One type of cone cell is most sensitive to short wavelengths (blue light), another is most sensitive to medium wavelengths (green light), and the third is most sensitive to long wavelengths (red light). When light enters the eye, it is absorbed by these pigments in the cones, which then send signals to the brain. The brain interprets these signals and translates them into the perception of color.

People with normal color vision can distinguish between millions of different colors based on the specific combinations of wavelengths that are present in a given scene. However, some people have deficiencies or abnormalities in their color vision, which can make it difficult or impossible to distinguish between certain colors. These conditions are known as color vision deficiencies or color blindness.

Strabismus is a condition of the ocular muscles where the eyes are not aligned properly and point in different directions. One eye may turn inward, outward, upward, or downward while the other one remains fixed and aligns normally. This misalignment can occur occasionally or constantly. Strabismus is also commonly referred to as crossed eyes or walleye. The condition can lead to visual impairments such as amblyopia (lazy eye) and depth perception problems if not treated promptly and effectively, usually through surgery, glasses, or vision therapy.

Intraocular lenses (IOLs) are artificial lens implants that are placed inside the eye during ophthalmic surgery, such as cataract removal. These lenses are designed to replace the natural lens of the eye that has become clouded or damaged, thereby restoring vision impairment caused by cataracts or other conditions.

There are several types of intraocular lenses available, including monofocal, multifocal, toric, and accommodative lenses. Monofocal IOLs provide clear vision at a single fixed distance, while multifocal IOLs offer clear vision at multiple distances. Toric IOLs are designed to correct astigmatism, and accommodative IOLs can change shape and position within the eye to allow for a range of vision.

The selection of the appropriate type of intraocular lens depends on various factors, including the patient's individual visual needs, lifestyle, and ocular health. The implantation procedure is typically performed on an outpatient basis and involves minimal discomfort or recovery time. Overall, intraocular lenses have become a safe and effective treatment option for patients with vision impairment due to cataracts or other eye conditions.

A cataract is a clouding of the natural lens in the eye that affects vision. This clouding can cause vision to become blurry, faded, or dim, making it difficult to see clearly. Cataracts are a common age-related condition, but they can also be caused by injury, disease, or medication use. In most cases, cataracts develop gradually over time and can be treated with surgery to remove the cloudy lens and replace it with an artificial one.

Low vision is a term used to describe significant visual impairment that cannot be corrected with standard glasses, contact lenses, medication or surgery. It is typically defined as visual acuity of less than 20/70 in the better-seeing eye after best correction, or a visual field of less than 20 degrees in the better-seeing eye.

People with low vision may have difficulty performing everyday tasks such as reading, recognizing faces, watching television, driving, or simply navigating their environment. They may also experience symptoms such as sensitivity to light, glare, or contrast, and may benefit from the use of visual aids, assistive devices, and rehabilitation services to help them maximize their remaining vision and maintain their independence.

Low vision can result from a variety of causes, including eye diseases such as macular degeneration, diabetic retinopathy, glaucoma, or cataracts, as well as congenital or inherited conditions, brain injuries, or aging. It is important for individuals with low vision to receive regular eye examinations and consult with a low vision specialist to determine the best course of treatment and management.

The geniculate bodies are part of the auditory pathway in the brainstem. They are two small, rounded eminences located on the lateral side of the upper pons, near the junction with the midbrain. The geniculate bodies are divided into an anterior and a posterior portion, known as the anterior and posterior geniculate bodies, respectively.

The anterior geniculate body receives inputs from the contralateral cochlear nucleus via the trapezoid body, and it is involved in the processing of sound localization. The posterior geniculate body receives inputs from the inferior colliculus via the lateral lemniscus and is involved in the processing of auditory information for conscious perception.

Overall, the geniculate bodies play a critical role in the processing and transmission of auditory information to higher brain areas for further analysis and interpretation.

A visual field test is a method used to measure an individual's entire scope of vision, which includes what can be seen straight ahead and in peripheral (or side) vision. During the test, the person being tested is asked to focus on a central point while gradually identifying the appearance of objects moving into their peripheral vision. The visual field test helps detect blind spots (scotomas) or gaps in the visual field, which can be caused by various conditions such as glaucoma, brain injury, optic nerve damage, or retinal disorders. It's an essential tool for diagnosing and monitoring eye-related diseases and conditions.

I'm sorry for any confusion, but "Optics and Photonics" is a broad field that encompasses various scientific and engineering disciplines. It doesn't have a specific medical definition, as it's not a term typically used in a medical context.

However, I can provide a general definition:

Optics is the study of light and its interactions with matter. This includes how light is produced, controlled, transmitted, and detected. It involves phenomena such as reflection, refraction, diffraction, and interference.

Photonics, on the other hand, is a branch of optics that deals with the generation, detection, and manipulation of individual photons, the basic units of light. Photonics is often applied to technologies such as lasers, fiber optics, and optical communications.

In a medical context, these fields might be used in various diagnostic and therapeutic applications, such as endoscopes, ophthalmic devices, laser surgery, and imaging technologies like MRI and CT scans. But the terms "Optics" and "Photonics" themselves are not medical conditions or treatments.

Visual perception refers to the ability to interpret and organize information that comes from our eyes to recognize and understand what we are seeing. It involves several cognitive processes such as pattern recognition, size estimation, movement detection, and depth perception. Visual perception allows us to identify objects, navigate through space, and interact with our environment. Deficits in visual perception can lead to learning difficulties and disabilities.

Optokinetic nystagmus (OKN) is a type of involuntary eye movement that occurs in response to large moving visual patterns. It serves as a mechanism for stabilizing the image on the retina during head movement and helps in maintaining visual fixation.

In OKN, there are two phases of eye movement: a slow phase where the eyes follow or track the moving pattern, and a fast phase where the eyes quickly reset to the starting position. This results in a back-and-forth or "to-and-fro" motion of the eyes.

Optokinetic nystagmus can be elicited by observing a large moving object or a series of alternating visual stimuli, such as stripes on a rotating drum. It is often used in clinical settings to assess various aspects of the visual system, including oculomotor function and visual acuity.

Abnormalities in OKN can indicate problems with the vestibular system, brainstem, or cerebellum, and may be associated with conditions such as brain injury, multiple sclerosis, or cerebral palsy.

Eyeglasses are a medical device used to correct vision problems. Also known as spectacles, they consist of frames that hold one or more lenses through which a person looks to see clearly. The lenses may be made of glass or plastic and are designed to compensate for various visual impairments such as nearsightedness, farsightedness, astigmatism, or presbyopia. Eyeglasses can be custom-made to fit an individual's face and prescription, and they come in a variety of styles, colors, and materials. Some people wear eyeglasses all the time, while others may only need to wear them for certain activities such as reading or driving.

The retina is the innermost, light-sensitive layer of tissue in the eye of many vertebrates and some cephalopods. It receives light that has been focused by the cornea and lens, converts it into neural signals, and sends these to the brain via the optic nerve. The retina contains several types of photoreceptor cells including rods (which handle vision in low light) and cones (which are active in bright light and are capable of color vision).

In medical terms, any pathological changes or diseases affecting the retinal structure and function can lead to visual impairment or blindness. Examples include age-related macular degeneration, diabetic retinopathy, retinal detachment, and retinitis pigmentosa among others.

Laser In Situ Keratomileusis (LASIK) is a type of refractive surgery used to correct vision issues such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism. The procedure involves reshaping the cornea, which is the clear, dome-shaped surface at the front of the eye, using an excimer laser.

In LASIK, a thin flap is created on the surface of the cornea using a femtosecond or microkeratome laser. The flap is then lifted, and the excimer laser is used to reshape the underlying tissue. After the reshaping is complete, the flap is replaced, allowing for quicker healing and visual recovery compared to other refractive surgery procedures.

LASIK is an outpatient procedure that typically takes about 30 minutes or less per eye. Most people can expect to see improved vision within a few days of the procedure, although it may take several weeks for vision to fully stabilize. LASIK has a high success rate and is generally considered safe when performed by a qualified surgeon. However, as with any surgical procedure, there are risks involved, including dry eye, infection, and visual complications such as glare or halos around lights.

Perceptual disorders are conditions that affect the way a person perceives or interprets sensory information from their environment. These disorders can involve any of the senses, including sight, sound, touch, taste, and smell. They can cause a person to have difficulty recognizing, interpreting, or responding appropriately to sensory stimuli.

Perceptual disorders can result from damage to the brain or nervous system, such as from a head injury, stroke, or degenerative neurological condition. They can also be caused by certain mental health conditions, such as schizophrenia or severe depression.

Symptoms of perceptual disorders may include:

* Misinterpretations of sensory information, such as seeing things that are not there or hearing voices that are not present
* Difficulty recognizing familiar objects or people
* Problems with depth perception or spatial awareness
* Difficulty judging the size, shape, or distance of objects
* Trouble distinguishing between similar sounds or colors
* Impaired sense of smell or taste

Perceptual disorders can have a significant impact on a person's daily life and functioning. Treatment may involve medication, therapy, or rehabilitation to help the person better cope with their symptoms and improve their ability to interact with their environment.

A scotoma is a blind spot or area of reduced vision within the visual field. It's often surrounded by an area of less distinct vision and can be caused by various conditions such as eye diseases, neurological disorders, or brain injuries. A scotoma may be temporary or permanent, depending on its underlying cause.

There are different types of scotomas, including:

1. Central scotoma - a blind spot in the center of the visual field, often associated with conditions like age-related macular degeneration and diabetic retinopathy.
2. Paracentral scotoma - a blind spot located slightly away from the center of the visual field, which can be caused by optic neuritis or other optic nerve disorders.
3. Peripheral scotoma - a blind spot in the peripheral vision, often associated with retinal diseases like retinitis pigmentosa.
4. Absolute scotoma - a complete loss of vision in a specific area of the visual field.
5. Relative scotoma - a partial loss of vision in which some details can still be perceived, but not as clearly or vividly as in normal vision.

It is essential to consult an eye care professional if you experience any changes in your vision or notice a scotoma, as early detection and treatment can help prevent further vision loss.

Dark adaptation is the process by which the eyes adjust to low levels of light. This process allows the eyes to become more sensitive to light and see better in the dark. It involves the dilation of the pupils, as well as chemical changes in the rods and cones (photoreceptor cells) of the retina. These changes allow the eye to detect even small amounts of light and improve visual acuity in low-light conditions. Dark adaptation typically takes several minutes to occur fully, but can be faster or slower depending on various factors such as age, prior exposure to light, and certain medical conditions. It is an important process for maintaining good vision in a variety of lighting conditions.

Optic neuritis is a medical condition characterized by inflammation and damage to the optic nerve, which transmits visual information from the eye to the brain. This condition can result in various symptoms such as vision loss, pain with eye movement, color vision disturbances, and pupillary abnormalities. Optic neuritis may occur in isolation or be associated with other underlying medical conditions, including multiple sclerosis, neuromyelitis optica, and autoimmune disorders. The diagnosis typically involves a comprehensive eye examination, including visual acuity testing, dilated funduscopic examination, and possibly imaging studies like MRI to evaluate the optic nerve and brain. Treatment options may include corticosteroids or other immunomodulatory therapies to reduce inflammation and prevent further damage to the optic nerve.

In a medical context, "orientation" typically refers to an individual's awareness and understanding of their personal identity, place, time, and situation. It is a critical component of cognitive functioning and mental status. Healthcare professionals often assess a person's orientation during clinical evaluations, using tests that inquire about their name, location, the current date, and the circumstances of their hospitalization or visit.

There are different levels of orientation:

1. Person (or self): The individual knows their own identity, including their name, age, and other personal details.
2. Place: The individual is aware of where they are, such as the name of the city, hospital, or healthcare facility.
3. Time: The individual can accurately state the current date, day of the week, month, and year.
4. Situation or event: The individual understands why they are in the healthcare setting, what happened leading to their hospitalization or visit, and the nature of any treatments or procedures they are undergoing.

Impairments in orientation can be indicative of various neurological or psychiatric conditions, such as delirium, dementia, or substance intoxication or withdrawal. It is essential for healthcare providers to monitor and address orientation issues to ensure appropriate diagnosis, treatment, and patient safety.

I'm sorry for any confusion, but "lighting" does not have a specific medical definition. In a general context, lighting refers to the arrangement or use of light sources to achieve a particular effect or atmosphere. However, if you are referring to a term in medicine that may be similar to "lighting," you might be thinking of "lumination" or "illumination," which refer to the act of providing or admitting light, especially for medical examination or surgical procedures. I hope this helps! If you have any other questions, please don't hesitate to ask.

Ocular refraction is a medical term that refers to the bending of light as it passes through the optical media of the eye, including the cornea and lens. This process allows the eye to focus light onto the retina, creating a clear image. The refractive power of the eye is determined by the curvature and transparency of these structures.

In a normal eye, light rays are bent or refracted in such a way that they converge at a single point on the retina, producing a sharp and focused image. However, if the curvature of the cornea or lens is too steep or too flat, the light rays may not converge properly, resulting in a refractive error such as myopia (nearsightedness), hyperopia (farsightedness), or astigmatism.

Ocular refraction can be measured using a variety of techniques, including retinoscopy, automated refraction, and subjective refraction. These measurements are used to determine the appropriate prescription for corrective lenses such as eyeglasses or contact lenses. In some cases, ocular refractive errors may be corrected surgically through procedures such as LASIK or PRK.

"Macaca nemestrina," also known as the pig-tailed macaque, is not a medical term but a species name in biology. It refers to a specific species of monkey that is native to Southeast Asia. The pig-tailed macaque is a medium-sized monkey with a reddish-brown fur and a distinctive tail that resembles a pig's tail. They are omnivorous and live in social groups that can range from a few individuals to several hundred.

While "Macaca nemestrina" may not have a direct medical definition, these monkeys have been used as models in biomedical research due to their close genetic relationship with humans. Some studies involving pig-tailed macaques have contributed to our understanding of various human diseases and conditions, such as infectious diseases, neurological disorders, and reproductive health. However, it is important to note that the use of animals in research remains a controversial topic, and ethical considerations must be taken into account when conducting such studies.

Refractive errors are a group of vision conditions that include nearsightedness (myopia), farsightedness (hyperopia), astigmatism, and presbyopia. These conditions occur when the shape of the eye prevents light from focusing directly on the retina, causing blurred or distorted vision.

Myopia is a condition where distant objects appear blurry while close-up objects are clear. This occurs when the eye is too long or the cornea is too curved, causing light to focus in front of the retina instead of directly on it.

Hyperopia, on the other hand, is a condition where close-up objects appear blurry while distant objects are clear. This happens when the eye is too short or the cornea is not curved enough, causing light to focus behind the retina.

Astigmatism is a condition that causes blurred vision at all distances due to an irregularly shaped cornea or lens.

Presbyopia is a natural aging process that affects everyone as they get older, usually around the age of 40. It causes difficulty focusing on close-up objects and can be corrected with reading glasses, bifocals, or progressive lenses.

Refractive errors can be diagnosed through a comprehensive eye exam and are typically corrected with eyeglasses, contact lenses, or refractive surgery such as LASIK.

Monocular vision refers to the ability to see and process visual information using only one eye. It is the type of vision that an individual has when they are using only one eye to look at something, while the other eye may be covered or not functioning. This can be contrasted with binocular vision, which involves the use of both eyes working together to provide depth perception and a single, combined visual field.

Monocular vision is important for tasks that only require the use of one eye, such as when looking through a microscope or using a telescope. However, it does not provide the same level of depth perception and spatial awareness as binocular vision. In some cases, individuals may have reduced visual acuity or other visual impairments in one eye, leading to limited monocular vision in that eye. It is important for individuals with monocular vision to have regular eye exams to monitor their eye health and ensure that any visual impairments are detected and treated promptly.

Ocular accommodation is the process by which the eye changes optical power to maintain a clear image or focus on an object as its distance varies. This is primarily achieved by the lens of the eye changing shape through the action of the ciliary muscles inside the eye. When you look at something far away, the lens becomes flatter, and when you look at something close up, the lens thickens. This ability to adjust focus allows for clear vision at different distances.

Motion perception is the ability to interpret and understand the movement of objects in our environment. It is a complex process that involves multiple areas of the brain and the visual system. In medical terms, motion perception refers to the specific function of the visual system to detect and analyze the movement of visual stimuli. This allows us to perceive and respond to moving objects in our environment, which is crucial for activities such as driving, sports, and even maintaining balance. Disorders in motion perception can lead to conditions like motion sickness or difficulty with depth perception.

The visual cortex is the part of the brain that processes visual information. It is located in the occipital lobe, which is at the back of the brain. The visual cortex is responsible for receiving and interpreting signals from the retina, which are then transmitted through the optic nerve and optic tract.

The visual cortex contains several areas that are involved in different aspects of visual processing, such as identifying shapes, colors, and movements. These areas work together to help us recognize and understand what we see. Damage to the visual cortex can result in various visual impairments, such as blindness or difficulty with visual perception.

Retinal cone photoreceptor cells are specialized neurons located in the retina of the eye, responsible for visual phototransduction and color vision. They are one of the two types of photoreceptors, with the other being rods, which are more sensitive to low light levels. Cones are primarily responsible for high-acuity, color vision during daylight or bright-light conditions.

There are three types of cone cells, each containing different photopigments that absorb light at distinct wavelengths: short (S), medium (M), and long (L) wavelengths, which correspond to blue, green, and red light, respectively. The combination of signals from these three types of cones allows the human visual system to perceive a wide range of colors and discriminate between them. Cones are densely packed in the central region of the retina, known as the fovea, which provides the highest visual acuity.

"Ocular physiological phenomena" is not a standardized medical term with a specific definition. However, I can provide some examples of ocular physiological phenomena, which refer to various normal functions and processes that occur in the eye. Here are a few examples:

1. Accommodation: The ability of the eye to change optical power to maintain a clear image or focus on an object as its distance varies. This is primarily achieved by changing the curvature of the lens through the action of the ciliary muscles.
2. Pupillary reflex: The automatic adjustment of the pupil's size in response to changes in light intensity. In bright light, the pupil constricts (miosis), while in dim light, it dilates (mydriasis). This reflex helps regulate the amount of light that enters the eye.
3. Tear production: The continuous secretion of tears by the lacrimal glands to keep the eyes moist and protected from dust, microorganisms, and other foreign particles.
4. Extraocular muscle function: The coordinated movement of the six extraocular muscles that control eyeball rotation and enable various gaze directions.
5. Color vision: The ability to perceive and distinguish different colors based on the sensitivity of photoreceptor cells (cones) in the retina to specific wavelengths of light.
6. Dark adaptation: The process by which the eyes adjust to low-light conditions, improving visual sensitivity primarily through changes in the rod photoreceptors' sensitivity and pupil dilation.
7. Light adaptation: The ability of the eye to adjust to different levels of illumination, mainly through alterations in pupil size and photoreceptor cell response.

These are just a few examples of ocular physiological phenomena. There are many more processes and functions that occur within the eye, contributing to our visual perception and overall eye health.

In the context of medical terminology, "light" doesn't have a specific or standardized definition on its own. However, it can be used in various medical terms and phrases. For example, it could refer to:

1. Visible light: The range of electromagnetic radiation that can be detected by the human eye, typically between wavelengths of 400-700 nanometers. This is relevant in fields such as ophthalmology and optometry.
2. Therapeutic use of light: In some therapies, light is used to treat certain conditions. An example is phototherapy, which uses various wavelengths of ultraviolet (UV) or visible light for conditions like newborn jaundice, skin disorders, or seasonal affective disorder.
3. Light anesthesia: A state of reduced consciousness in which the patient remains responsive to verbal commands and physical stimulation. This is different from general anesthesia where the patient is completely unconscious.
4. Pain relief using light: Certain devices like transcutaneous electrical nerve stimulation (TENS) units have a 'light' setting, indicating lower intensity or frequency of electrical impulses used for pain management.

Without more context, it's hard to provide a precise medical definition of 'light'.

Macular degeneration, also known as age-related macular degeneration (AMD), is a medical condition that affects the central part of the retina, called the macula. The macula is responsible for sharp, detailed vision, which is necessary for activities such as reading, driving, and recognizing faces.

In AMD, there is a breakdown or deterioration of the macula, leading to gradual loss of central vision. There are two main types of AMD: dry (atrophic) and wet (exudative). Dry AMD is more common and progresses more slowly, while wet AMD is less common but can cause rapid and severe vision loss if left untreated.

The exact causes of AMD are not fully understood, but risk factors include age, smoking, family history, high blood pressure, obesity, and exposure to sunlight. While there is no cure for AMD, treatments such as vitamin supplements, laser therapy, and medication injections can help slow its progression and reduce the risk of vision loss.

Glaucoma is a group of eye conditions that damage the optic nerve, often caused by an abnormally high pressure in the eye (intraocular pressure). This damage can lead to permanent vision loss or even blindness if left untreated. The most common type is open-angle glaucoma, which has no warning signs and progresses slowly. Angle-closure glaucoma, on the other hand, can cause sudden eye pain, redness, nausea, and vomiting, as well as rapid vision loss. Other less common types of glaucoma also exist. While there is no cure for glaucoma, early detection and treatment can help slow or prevent further vision loss.

Dyslexia is a neurodevelopmental disorder that impairs an individual's ability to read, write, and spell, despite having normal intelligence and adequate education. It is characterized by difficulties with accurate and fluent word recognition, poor decoding and spelling abilities, and often accompanied by problems with reading comprehension and reduced reading experience. Dyslexia is not a result of low intelligence, lack of motivation, or poor instruction, but rather a specific learning disability that affects the way the brain processes written language. It is typically diagnosed in children, although it can go unnoticed until adulthood, and there are effective interventions and accommodations to help individuals with dyslexia overcome their challenges and achieve academic and professional success.

Medical definitions for visual impairment often vary, but according to the World Health Organization (WHO), visually impaired persons are those who have a best-corrected visual acuity of less than 0.3 (6/12) in their better eye or a visual field of less than 20 degrees in their better eye. This includes people who are blind, as well as those with partial sight.

Visual impairment can range from mild to severe and may result from a variety of causes, including genetic disorders, diseases, trauma, or aging. It is important to note that visual impairment does not necessarily mean total blindness; many visually impaired individuals have some remaining vision and can benefit from low vision services and assistive devices.

Depth perception is the ability to accurately judge the distance or separation of an object in three-dimensional space. It is a complex visual process that allows us to perceive the world in three dimensions and to understand the spatial relationships between objects.

Depth perception is achieved through a combination of monocular cues, which are visual cues that can be perceived with one eye, and binocular cues, which require input from both eyes. Monocular cues include perspective (the relative size of objects), texture gradients (finer details become smaller as distance increases), and atmospheric perspective (colors become less saturated and lighter in value as distance increases). Binocular cues include convergence (the degree to which the eyes must turn inward to focus on an object) and retinal disparity (the slight difference in the images projected onto the two retinas due to the slightly different positions of the eyes).

Deficits in depth perception can occur due to a variety of factors, including eye disorders, brain injuries, or developmental delays. These deficits can result in difficulties with tasks such as driving, sports, or navigating complex environments. Treatment for depth perception deficits may include vision therapy, corrective lenses, or surgery.

Vision screening is a quick and cost-effective method used to identify individuals who are at risk of vision problems or eye diseases. It is not a comprehensive eye examination, but rather an initial evaluation that helps to determine if a further, more in-depth examination by an eye care professional is needed. Vision screenings typically involve tests for visual acuity, distance and near vision, color perception, depth perception, and alignment of the eyes. The goal of vision screening is to detect potential vision issues early on, so that they can be treated promptly and effectively, thereby preventing or minimizing any negative impact on a person's overall vision and quality of life.

Anisometropia is a medical term that refers to a condition where there is a significant difference in the refractive power between the two eyes. In other words, one eye has a significantly different optical prescription compared to the other eye. This condition can cause issues with binocular vision and depth perception, and can sometimes lead to amblyopia (lazy eye) if not corrected early in life. It is typically diagnosed through a comprehensive eye examination and can be corrected with glasses or contact lenses.

Ocular fixation is a term used in ophthalmology and optometry to refer to the ability of the eyes to maintain steady gaze or visual focus on an object. It involves the coordinated movement of the extraocular muscles that control eye movements, allowing for clear and stable vision.

In medical terminology, fixation specifically refers to the state in which the eyes are aligned and focused on a single point in space. This is important for maintaining visual perception and preventing blurring or double vision. Ocular fixation can be affected by various factors such as muscle weakness, nerve damage, or visual processing disorders.

Assessment of ocular fixation is often used in eye examinations to evaluate visual acuity, eye alignment, and muscle function. Abnormalities in fixation may indicate the presence of underlying eye conditions or developmental delays that require further investigation and treatment.

Sensory deprivation, also known as perceptual isolation or sensory restriction, refers to the deliberate reduction or removal of stimuli from one or more of the senses. This can include limiting input from sight, sound, touch, taste, and smell. The goal is to limit a person's sensory experiences in order to study the effects on cognition, perception, and behavior.

In a clinical context, sensory deprivation can occur as a result of certain medical conditions or treatments, such as blindness, deafness, or pharmacological interventions that affect sensory processing. Prolonged sensory deprivation can lead to significant psychological and physiological effects, including hallucinations, delusions, and decreased cognitive function.

It's important to note that sensory deprivation should not be confused with meditation or relaxation techniques that involve reducing external stimuli in a controlled manner to promote relaxation and focus.

Aging is a complex, progressive and inevitable process of bodily changes over time, characterized by the accumulation of cellular damage and degenerative changes that eventually lead to increased vulnerability to disease and death. It involves various biological, genetic, environmental, and lifestyle factors that contribute to the decline in physical and mental functions. The medical field studies aging through the discipline of gerontology, which aims to understand the underlying mechanisms of aging and develop interventions to promote healthy aging and extend the human healthspan.

Open-angle glaucoma is a chronic, progressive type of glaucoma characterized by the gradual loss of optic nerve fibers and resulting in visual field defects. It is called "open-angle" because the angle where the iris meets the cornea (trabecular meshwork) appears to be normal and open on examination. The exact cause of this condition is not fully understood, but it is associated with increased resistance to the outflow of aqueous humor within the trabecular meshwork, leading to an increase in intraocular pressure (IOP). This elevated IOP can cause damage to the optic nerve and result in vision loss.

The onset of open-angle glaucoma is often asymptomatic, making regular comprehensive eye examinations crucial for early detection and management. Treatment typically involves lowering IOP using medications, laser therapy, or surgery to prevent further optic nerve damage and preserve vision.

Fluspirilene is an antipsychotic medication that belongs to the diphenylbutylpiperidine class. It works by blocking dopamine receptors in the brain, which helps to reduce psychosis, agitation, and hostility in people with schizophrenia. Fluspirilene has a long duration of action, with its effects lasting up to several weeks after a single injection.

Here is the medical definition of Fluspirilene:

Fluspirilene: A diphenylbutylpiperidine antipsychotic drug used in the treatment of chronic schizophrenia. It has a long duration of action, with therapeutic effects persisting for up to 4 weeks after a single injection. Fluspirilene works by blocking dopamine receptors in the brain, which helps to reduce psychosis, agitation, and hostility. Common side effects include extrapyramidal symptoms (EPS), such as tremors, rigidity, and akathisia, as well as weight gain, sedation, and sexual dysfunction. Fluspirilene is available in the form of a depot injection for intramuscular use.

Photometry is the measurement and study of light, specifically its brightness or luminous intensity. In a medical context, photometry is often used in ophthalmology to describe diagnostic tests that measure the amount and type of light that is perceived by the eye. This can help doctors diagnose and monitor various eye conditions and diseases, such as cataracts, glaucoma, and retinal disorders. Photometry may also be used in other medical fields, such as dermatology, to evaluate the effects of different types of light on skin conditions.

Astigmatism is a common eye condition that occurs when the cornea or lens has an irregular shape, causing blurred or distorted vision. The cornea and lens are typically smooth and curved uniformly in all directions, allowing light to focus clearly on the retina. However, if the cornea or lens is not smoothly curved and has a steeper curve in one direction than the other, it causes light to focus unevenly on the retina, leading to astigmatism.

Astigmatism can cause blurred vision at all distances, as well as eye strain, headaches, and fatigue. It is often present from birth and can be hereditary, but it can also develop later in life due to eye injuries or surgery. Astigmatism can be corrected with glasses, contact lenses, or refractive surgery such as LASIK.

Mesopic vision is a term used to describe the intermediate level of vision that occurs in conditions of decreased illumination, specifically between 0.02 and 3 candelas per square meter (cd/m²). This range falls between photopic vision, which is vision in bright light (>3 cd/m²), and scotopic vision, which is vision in very low light (

Contact lenses are thin, curved plastic or silicone hydrogel devices that are placed on the eye to correct vision, replace a missing or damaged cornea, or for cosmetic purposes. They rest on the surface of the eye, called the cornea, and conform to its shape. Contact lenses are designed to float on a thin layer of tears and move with each blink.

There are two main types of contact lenses: soft and rigid gas permeable (RGP). Soft contact lenses are made of flexible hydrophilic (water-absorbing) materials that allow oxygen to pass through the lens to the cornea. RGP lenses are made of harder, more oxygen-permeable materials.

Contact lenses can be used to correct various vision problems, including nearsightedness, farsightedness, astigmatism, and presbyopia. They come in different shapes, sizes, and powers to suit individual needs and preferences. Proper care, handling, and regular check-ups with an eye care professional are essential for maintaining good eye health and preventing complications associated with contact lens wear.

"Cat" is a common name that refers to various species of small carnivorous mammals that belong to the family Felidae. The domestic cat, also known as Felis catus or Felis silvestris catus, is a popular pet and companion animal. It is a subspecies of the wildcat, which is found in Europe, Africa, and Asia.

Domestic cats are often kept as pets because of their companionship, playful behavior, and ability to hunt vermin. They are also valued for their ability to provide emotional support and therapy to people. Cats are obligate carnivores, which means that they require a diet that consists mainly of meat to meet their nutritional needs.

Cats are known for their agility, sharp senses, and predatory instincts. They have retractable claws, which they use for hunting and self-defense. Cats also have a keen sense of smell, hearing, and vision, which allow them to detect prey and navigate their environment.

In medical terms, cats can be hosts to various parasites and diseases that can affect humans and other animals. Some common feline diseases include rabies, feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), and toxoplasmosis. It is important for cat owners to keep their pets healthy and up-to-date on vaccinations and preventative treatments to protect both the cats and their human companions.

Orthokeratology, often referred to as "ortho-k," is a non-surgical procedure that uses specially designed contact lenses to temporarily reshape the cornea (the clear, dome-shaped surface at the front of the eye). The goal of orthokeratology is to flatten the cornea slightly so that it can properly focus light onto the retina and improve vision.

During an orthokeratology procedure, a patient wears specially fitted contact lenses while they sleep. These lenses gently reshape the cornea overnight, allowing the patient to see clearly during the day without needing glasses or contact lenses. The effects of orthokeratology are usually reversible and may wear off if the patient stops wearing the contact lenses regularly.

Orthokeratology is often used as an alternative to refractive surgery for people who want to correct their vision without undergoing a surgical procedure. It can be particularly useful for individuals with mild to moderate myopia (nearsightedness) and astigmatism, although it may also be used to treat other refractive errors.

It's important to note that orthokeratology is not a permanent solution for vision problems, and it does carry some risks, such as eye infections and corneal abrasions. As with any medical procedure, it's essential to consult with an eye care professional to determine whether orthokeratology is the right choice for you.

An afterimage is a visual phenomenon that occurs when the eye's retina continues to send signals to the brain even after exposure to a stimulus has ended. This can result in the perception of a lingering image, often in complementary colors to the original stimulus. Afterimages can be either positive or negative, with a positive afterimage appearing as the same color as the original stimulus and a negative afterimage appearing as its complementary color.

Afterimages are typically caused by exposure to bright or intense light sources, such as a camera flash or the sun. They can also occur after prolonged exposure to a particular color or pattern. The phenomenon is thought to be related to the adaptation of photoreceptor cells in the retina, which become less responsive to stimuli after prolonged exposure.

Afterimages are generally harmless and temporary, lasting only a few seconds to several minutes. However, they can sometimes be used as a tool for visual perception experiments or to study the mechanisms of visual processing in the brain.

Psychophysiology is a branch of psychology that deals with the scientific study of the relationships between physical processes (such as heart rate, skin conductance, brain activity) and mental or emotional states. It involves the use of physiological measures to understand psychological phenomena and how they relate to behavior. This field of study often employs various research methods, including laboratory experiments, observational studies, and neuroimaging techniques, to examine these relationships in both healthy individuals and those with psychological disorders. The goal of psychophysiology is to better understand the underlying mechanisms that contribute to emotional, cognitive, and behavioral functioning.

Optic nerve diseases refer to a group of conditions that affect the optic nerve, which transmits visual information from the eye to the brain. These diseases can cause various symptoms such as vision loss, decreased visual acuity, changes in color vision, and visual field defects. Examples of optic nerve diseases include optic neuritis (inflammation of the optic nerve), glaucoma (damage to the optic nerve due to high eye pressure), optic nerve damage from trauma or injury, ischemic optic neuropathy (lack of blood flow to the optic nerve), and optic nerve tumors. Treatment for optic nerve diseases varies depending on the specific condition and may include medications, surgery, or lifestyle changes.

Psychological models are theoretical frameworks used in psychology to explain and predict mental processes and behaviors. They are simplified representations of complex phenomena, consisting of interrelated concepts, assumptions, and hypotheses that describe how various factors interact to produce specific outcomes. These models can be quantitative (e.g., mathematical equations) or qualitative (e.g., conceptual diagrams) in nature and may draw upon empirical data, theoretical insights, or both.

Psychological models serve several purposes:

1. They provide a systematic and organized way to understand and describe psychological phenomena.
2. They generate hypotheses and predictions that can be tested through empirical research.
3. They integrate findings from different studies and help synthesize knowledge across various domains of psychology.
4. They inform the development of interventions and treatments for mental health disorders.

Examples of psychological models include:

1. The Five Factor Model (FFM) of personality, which posits that individual differences in personality can be described along five broad dimensions: Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism.
2. The Cognitive-Behavioral Therapy (CBT) model, which suggests that maladaptive thoughts, feelings, and behaviors are interconnected and can be changed through targeted interventions.
3. The Dual Process Theory of Attitudes, which proposes that attitudes are formed and influenced by two distinct processes: a rapid, intuitive process (heuristic) and a slower, deliberative process (systematic).
4. The Social Cognitive Theory, which emphasizes the role of observational learning, self-efficacy, and outcome expectations in shaping behavior.
5. The Attachment Theory, which describes the dynamics of long-term relationships between humans, particularly the parent-child relationship.

It is important to note that psychological models are provisional and subject to revision or replacement as new evidence emerges. They should be considered as useful tools for understanding and explaining psychological phenomena rather than definitive truths.

Aberrometry is a medical diagnostic technique used to measure the amount and type of aberration or distortion in the optical system of the eye. It is often used to evaluate the quality of vision, particularly in cases where traditional methods of measuring visual acuity are not sufficient.

During an aberrometry test, the patient looks into a specialized instrument called a wavefront sensor while a series of light patterns are projected onto the retina. The sensor then measures how the light is distorted as it passes through the eye's optical system, including the cornea and lens. This information is used to create a detailed map of the eye's aberrations, which can help doctors identify any irregularities that may be contributing to visual symptoms such as blurred vision, glare, or halos around lights.

Aberrometry is often used in conjunction with other diagnostic tests to evaluate patients who are considering refractive surgery, such as LASIK or PRK. By identifying any abnormalities in the eye's optical system, doctors can determine whether a patient is a good candidate for surgery and make more informed decisions about how to proceed with treatment.

Ethylamines are organic compounds that contain a primary amino group (-NH2) attached to an ethyl group (-C2H5). In other words, they have the formula R-CH2-CH2-NH2, where R is a carbon-containing group. Ethylamines are derivatives of ammonia (NH3), in which one or more hydrogen atoms have been replaced by an ethyl group.

Ethylamines can be found in various natural and synthetic substances. They are used as building blocks in the synthesis of various pharmaceuticals, agrochemicals, and other industrial chemicals. Some ethylamines also have psychoactive properties and are used as recreational drugs or abused for their mind-altering effects.

It is important to note that some ethylamines can be toxic or harmful to human health, especially at high concentrations or with prolonged exposure. Therefore, they should be handled with care and used only under controlled conditions.

Cataract extraction is a surgical procedure that involves removing the cloudy lens (cataract) from the eye. This procedure is typically performed to restore vision impairment caused by cataracts and improve overall quality of life. There are two primary methods for cataract extraction:

1. Phacoemulsification: This is the most common method used today. It involves making a small incision in the front part of the eye (cornea), inserting an ultrasonic probe to break up the cloudy lens into tiny pieces, and then removing those pieces with suction. After removing the cataract, an artificial intraocular lens (IOL) is inserted to replace the natural lens and help focus light onto the retina.

2. Extracapsular Cataract Extraction: In this method, a larger incision is made on the side of the cornea, allowing the surgeon to remove the cloudy lens in one piece without breaking it up. The back part of the lens capsule is left intact to support the IOL. This technique is less common and typically reserved for more advanced cataracts or when phacoemulsification cannot be performed.

Recovery from cataract extraction usually involves using eye drops to prevent infection and inflammation, as well as protecting the eye with a shield or glasses during sleep for a few weeks after surgery. Most people experience improved vision within a few days to a week following the procedure.

Size perception in a medical context typically refers to the way an individual's brain interprets and perceives the size or volume of various stimuli. This can include visual stimuli, such as objects or distances, as well as tactile stimuli, like the size of an object being held or touched.

Disorders in size perception can occur due to neurological conditions, brain injuries, or certain developmental disorders. For example, individuals with visual agnosia may have difficulty recognizing or perceiving the size of objects they see, even though their eyes are functioning normally. Similarly, those with somatoparaphrenia may not recognize the size of their own limbs due to damage in specific areas of the brain.

It's important to note that while 'size perception' is not a medical term per se, it can still be used in a medical or clinical context to describe these types of symptoms and conditions.

Retinal Ganglion Cells (RGCs) are a type of neuron located in the innermost layer of the retina, the light-sensitive tissue at the back of the eye. These cells receive visual information from photoreceptors (rods and cones) via intermediate cells called bipolar cells. RGCs then send this visual information through their long axons to form the optic nerve, which transmits the signals to the brain for processing and interpretation as vision.

There are several types of RGCs, each with distinct morphological and functional characteristics. Some RGCs are specialized in detecting specific features of the visual scene, such as motion, contrast, color, or brightness. The diversity of RGCs allows for a rich and complex representation of the visual world in the brain.

Damage to RGCs can lead to various visual impairments, including loss of vision, reduced visual acuity, and altered visual fields. Conditions associated with RGC damage or degeneration include glaucoma, optic neuritis, ischemic optic neuropathy, and some inherited retinal diseases.

Argon is a colorless, odorless, tasteless, and nonreactive noble gas that occurs in the Earth's atmosphere. It is chemically inert and is extracted from air by fractional distillation. Argon is used in various applications such as illumination, welding, and as a shielding gas in manufacturing processes.

In medical terms, argon is not commonly used as a therapeutic agent or medication. However, it has been used in some medical procedures such as argon laser therapy for the treatment of certain eye conditions like diabetic retinopathy and age-related macular degeneration. In these procedures, an argon laser is used to seal off leaking blood vessels or destroy abnormal tissue in the eye.

Overall, while argon has important uses in medical procedures, it is not a medication or therapeutic agent that is commonly administered directly to patients.

The medical definition of 'Automobile Driving' is the act of operating a motor vehicle, typically a car, on public roads or highways. This requires a set of cognitive, physical, and sensory skills to safely control the vehicle, navigate through traffic, and respond to various situations that may arise while driving.

Cognitive skills include attention, memory, decision-making, problem-solving, and judgment. Physical abilities encompass fine motor coordination, reaction time, strength, and flexibility. Sensory functions such as vision, hearing, and touch are also essential for safe driving.

Various medical conditions or medications can impair these skills and affect a person's ability to drive safely. Therefore, it is crucial for individuals to consult with their healthcare providers about any potential risks associated with driving and follow any recommended restrictions or guidelines.

In the context of medical terminology, 'color' is not defined specifically with a unique meaning. Instead, it generally refers to the characteristic or appearance of something, particularly in relation to the color that a person may observe visually. For instance, doctors may describe the color of a patient's skin, eyes, hair, or bodily fluids to help diagnose medical conditions or monitor their progression.

For example, jaundice is a yellowing of the skin and whites of the eyes that can indicate liver problems, while cyanosis refers to a bluish discoloration of the skin and mucous membranes due to insufficient oxygen in the blood. Similarly, doctors may describe the color of stool or urine to help diagnose digestive or kidney issues.

Therefore, 'color' is not a medical term with a specific definition but rather a general term used to describe various visual characteristics of the body and bodily fluids that can provide important diagnostic clues for healthcare professionals.

Subretinal fluid (SRF) refers to the abnormal accumulation of fluid between the neurosensory retina and the pigment epithelium of the eye. This can occur due to various conditions such as age-related macular degeneration, central serous chorioretinopathy, or retinal detachment. The presence of subretinal fluid can distort vision and may require medical intervention depending on the underlying cause and severity of the condition.

In the context of medical terminology, "nature" is not typically used as a defined term. However, it can be used in various phrases to describe different concepts. For example:

1. By nature: This phrase is used to refer to an inherent or essential characteristic of something or someone. For instance, a person's natural disposition or the natural course of a disease.
2. Nature of illness/injury: This refers to the classification, characteristics, and features of a medical condition or trauma.
3. Human nature: This phrase is used to describe the inherent characteristics, tendencies, or instincts of human beings as a species.
4. Mother Nature: Although not a medical term, it is often used metaphorically to refer to the natural world or environment and its forces, which can have significant impacts on health and well-being.

In summary, while "nature" itself does not have a specific medical definition, it is used in various phrases within the medical field to convey different concepts related to inherent characteristics, classifications, and environmental factors that influence health and disease.

Presbyopia is a age-related eye condition, typically occurring after the age of 40, where the lens of the eye loses its flexibility and makes it difficult to focus on near objects. This results in blurred vision when reading, sewing or focusing on other close-up tasks. It's a natural part of the aging process and is not a disease. Corrective measures such as reading glasses, bifocals, multifocal lenses or contact lenses, or refractive surgery can help manage this condition.

Reproducibility of results in a medical context refers to the ability to obtain consistent and comparable findings when a particular experiment or study is repeated, either by the same researcher or by different researchers, following the same experimental protocol. It is an essential principle in scientific research that helps to ensure the validity and reliability of research findings.

In medical research, reproducibility of results is crucial for establishing the effectiveness and safety of new treatments, interventions, or diagnostic tools. It involves conducting well-designed studies with adequate sample sizes, appropriate statistical analyses, and transparent reporting of methods and findings to allow other researchers to replicate the study and confirm or refute the results.

The lack of reproducibility in medical research has become a significant concern in recent years, as several high-profile studies have failed to produce consistent findings when replicated by other researchers. This has led to increased scrutiny of research practices and a call for greater transparency, rigor, and standardization in the conduct and reporting of medical research.

Refractive surgical procedures are a type of ophthalmic surgery aimed at improving the refractive state of the eye and reducing or eliminating the need for corrective eyewear. These procedures reshape the cornea or alter the lens of the eye to correct nearsightedness (myopia), farsightedness (hyperopia), presbyopia, or astigmatism.

Examples of refractive surgical procedures include:

1. Laser-assisted in situ keratomileusis (LASIK): A laser is used to create a thin flap in the cornea, which is then lifted to allow reshaping of the underlying tissue with another laser. The flap is replaced, and the procedure is completed.
2. Photorefractive keratectomy (PRK): This procedure involves removing the outer layer of the cornea (epithelium) and using a laser to reshape the underlying tissue. A bandage contact lens is placed over the eye to protect it during healing.
3. LASEK (laser-assisted subepithelial keratomileusis): Similar to LASIK, but instead of creating a flap, the epithelium is loosened with an alcohol solution and moved aside. The laser treatment is applied, and the epithelium is replaced.
4. Small Incision Lenticule Extraction (SMILE): A femtosecond laser creates a small lenticule within the cornea, which is then removed through a tiny incision. This procedure reshapes the cornea to correct refractive errors.
5. Refractive lens exchange (RLE): The eye's natural lens is removed and replaced with an artificial intraocular lens (IOL) to correct refractive errors, similar to cataract surgery.
6. Implantable contact lenses: A thin, foldable lens is placed between the iris and the natural lens or behind the iris to improve the eye's focusing power.

These procedures are typically performed on an outpatient basis and may require topical anesthesia (eye drops) or local anesthesia. Potential risks and complications include infection, dry eye, visual disturbances, and changes in night vision. It is essential to discuss these potential risks with your ophthalmologist before deciding on a refractive surgery procedure.

Electroretinography (ERG) is a medical test used to evaluate the functioning of the retina, which is the light-sensitive tissue located at the back of the eye. The test measures the electrical responses of the retina to light stimulation.

During the procedure, a special contact lens or electrode is placed on the surface of the eye to record the electrical activity generated by the retina's light-sensitive cells (rods and cones) and other cells in the retina. The test typically involves presenting different levels of flashes of light to the eye while the electrical responses are recorded.

The resulting ERG waveform provides information about the overall health and function of the retina, including the condition of the photoreceptors, the integrity of the inner retinal layers, and the health of the retinal ganglion cells. This test is often used to diagnose and monitor various retinal disorders, such as retinitis pigmentosa, macular degeneration, and diabetic retinopathy.

In the field of medicine, "time factors" refer to the duration of symptoms or time elapsed since the onset of a medical condition, which can have significant implications for diagnosis and treatment. Understanding time factors is crucial in determining the progression of a disease, evaluating the effectiveness of treatments, and making critical decisions regarding patient care.

For example, in stroke management, "time is brain," meaning that rapid intervention within a specific time frame (usually within 4.5 hours) is essential to administering tissue plasminogen activator (tPA), a clot-busting drug that can minimize brain damage and improve patient outcomes. Similarly, in trauma care, the "golden hour" concept emphasizes the importance of providing definitive care within the first 60 minutes after injury to increase survival rates and reduce morbidity.

Time factors also play a role in monitoring the progression of chronic conditions like diabetes or heart disease, where regular follow-ups and assessments help determine appropriate treatment adjustments and prevent complications. In infectious diseases, time factors are crucial for initiating antibiotic therapy and identifying potential outbreaks to control their spread.

Overall, "time factors" encompass the significance of recognizing and acting promptly in various medical scenarios to optimize patient outcomes and provide effective care.

Retinal diseases refer to a group of conditions that affect the retina, which is the light-sensitive tissue located at the back of the eye. The retina is responsible for converting light into electrical signals that are sent to the brain and interpreted as visual images. Retinal diseases can cause vision loss or even blindness, depending on their severity and location in the retina.

Some common retinal diseases include:

1. Age-related macular degeneration (AMD): A progressive disease that affects the central part of the retina called the macula, causing blurred or distorted vision.
2. Diabetic retinopathy: A complication of diabetes that can damage the blood vessels in the retina, leading to vision loss.
3. Retinal detachment: A serious condition where the retina becomes separated from its underlying tissue, requiring immediate medical attention.
4. Macular edema: Swelling or thickening of the macula due to fluid accumulation, which can cause blurred vision.
5. Retinitis pigmentosa: A group of inherited eye disorders that affect the retina's ability to respond to light, causing progressive vision loss.
6. Macular hole: A small break in the macula that can cause distorted or blurry vision.
7. Retinal vein occlusion: Blockage of the retinal veins that can lead to bleeding, swelling, and potential vision loss.

Treatment for retinal diseases varies depending on the specific condition and its severity. Some treatments include medication, laser therapy, surgery, or a combination of these options. Regular eye exams are essential for early detection and treatment of retinal diseases.

Diabetic retinopathy is a diabetes complication that affects the eyes. It's caused by damage to the blood vessels of the light-sensitive tissue at the back of the eye (retina).

At first, diabetic retinopathy may cause no symptoms or only mild vision problems. Eventually, it can cause blindness. The condition usually affects both eyes.

There are two main stages of diabetic retinopathy:

1. Early diabetic retinopathy. This is when the blood vessels in the eye start to leak fluid or bleed. You might not notice any changes in your vision at this stage, but it's still important to get treatment because it can prevent the condition from getting worse.
2. Advanced diabetic retinopathy. This is when new, abnormal blood vessels grow on the surface of the retina. These vessels can leak fluid and cause severe vision problems, including blindness.

Diabetic retinopathy can be treated with laser surgery, injections of medication into the eye, or a vitrectomy (a surgical procedure to remove the gel-like substance that fills the center of the eye). It's important to get regular eye exams to detect diabetic retinopathy early and get treatment before it causes serious vision problems.

Perceptual masking, also known as sensory masking or just masking, is a concept in sensory perception that refers to the interference in the ability to detect or recognize a stimulus (the target) due to the presence of another stimulus (the mask). This phenomenon can occur across different senses, including audition and vision.

In the context of hearing, perceptual masking occurs when one sound (the masker) makes it difficult to hear another sound (the target) because the two sounds are presented simultaneously or in close proximity to each other. The masker can make the target sound less detectable, harder to identify, or even completely inaudible.

There are different types of perceptual masking, including:

1. Simultaneous Masking: When the masker and target sounds occur at the same time.
2. Temporal Masking: When the masker sound precedes or follows the target sound by a short period. This type of masking can be further divided into forward masking (when the masker comes before the target) and backward masking (when the masker comes after the target).
3. Informational Masking: A more complex form of masking that occurs when the listener's cognitive processes, such as attention or memory, are affected by the presence of the masker sound. This type of masking can make it difficult to understand speech in noisy environments, even if the signal-to-noise ratio is favorable.

Perceptual masking has important implications for understanding and addressing hearing difficulties, particularly in situations with background noise or multiple sounds occurring simultaneously.

I'm sorry for any confusion, but "reading" is not a term that has a specific medical definition. Reading is the activity or process of deciphering and understanding written words or text. It is a fundamental skill in language acquisition and communication, and is not typically used in a medical context unless there is a concern related to reading difficulties or disorders, such as dyslexia. If you have any questions related to medical terminology or health concerns, I'd be happy to try to help answer those for you!

Halogens are a group of nonmetallic elements found in the seventh group of the periodic table. They include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Tennessine (Ts) is sometimes also classified as a halogen, although it has not been extensively studied.

In medical terms, halogens have various uses in medicine and healthcare. For example:

* Chlorine is used for disinfection and sterilization of surgical instruments, drinking water, and swimming pools. It is also used as a medication to treat certain types of anemia.
* Fluoride is added to drinking water and toothpaste to prevent dental caries (cavities) by strengthening tooth enamel.
* Iodine is used as a disinfectant, in medical imaging, and in the treatment of thyroid disorders.
* Bromine has been used in the past as a sedative and anticonvulsant, but its use in medicine has declined due to safety concerns.

Halogens are highly reactive and can be toxic or corrosive in high concentrations, so they must be handled with care in medical settings.

Aphakia, postcataract is a medical condition that refers to the absence of the lens in the eye after cataract surgery. A cataract is a clouding of the natural lens inside the eye that can cause vision loss. During cataract surgery, the cloudy lens is removed and replaced with an artificial lens implant. However, if there is a complication during the procedure and the artificial lens is not placed in the eye or if it becomes dislocated after surgery, then the patient will develop aphakia, postcataract.

Patients with aphakia, postcataract have poor vision and may experience symptoms such as blurry vision, glare, and halos around lights. They are also at an increased risk of developing glaucoma and retinal detachment. To correct the vision in patients with aphakia, they can wear special contact lenses or glasses with high-powered lenses, or undergo a secondary surgical procedure to implant an artificial lens in the eye.

In a medical or psychological context, attention is the cognitive process of selectively concentrating on certain aspects of the environment while ignoring other things. It involves focusing mental resources on specific stimuli, sensory inputs, or internal thoughts while blocking out irrelevant distractions. Attention can be divided into different types, including:

1. Sustained attention: The ability to maintain focus on a task or stimulus over time.
2. Selective attention: The ability to concentrate on relevant stimuli while ignoring irrelevant ones.
3. Divided attention: The capacity to pay attention to multiple tasks or stimuli simultaneously.
4. Alternating attention: The skill of shifting focus between different tasks or stimuli as needed.

Deficits in attention are common symptoms of various neurological and psychiatric conditions, such as ADHD, dementia, depression, and anxiety disorders. Assessment of attention is an essential part of neuropsychological evaluations and can be measured using various tests and tasks.

"Fundus Oculi" is a medical term that refers to the back part of the interior of the eye, including the optic disc, macula, fovea, retinal vasculature, and peripheral retina. It is the area where light is focused and then transmitted to the brain via the optic nerve, forming visual images. Examinations of the fundus oculi are crucial for detecting various eye conditions such as diabetic retinopathy, macular degeneration, glaucoma, and other retinal diseases. The examination is typically performed using an ophthalmoscope or a specialized camera called a retinal camera.

An ophthalmoscope is a medical device used by healthcare professionals to examine the interior structures of the eye, including the retina, optic disc, and vitreous humor. It consists of a handle with a battery-powered light source and a head that contains lenses for focusing. When placed in contact with the patient's dilated pupil, the ophthalmoscope allows the examiner to visualize the internal structures of the eye and assess their health. Ophthalmoscopes are commonly used in routine eye examinations, as well as in the diagnosis and management of various eye conditions and diseases.

Intraocular injections are a type of medical procedure where medication is administered directly into the eye. This technique is often used to deliver drugs that treat various eye conditions, such as age-related macular degeneration, diabetic retinopathy, and endophthalmitis. The most common type of intraocular injection is an intravitreal injection, which involves injecting medication into the vitreous cavity, the space inside the eye filled with a clear gel-like substance called the vitreous humor. This procedure is typically performed by an ophthalmologist in a clinical setting and may be repeated at regular intervals depending on the condition being treated.

Intraocular lens (IOL) implantation is a surgical procedure that involves placing a small artificial lens inside the eye to replace the natural lens that has been removed. This procedure is typically performed during cataract surgery, where the cloudy natural lens is removed and replaced with an IOL to restore clear vision.

During the procedure, a small incision is made in the eye, and the cloudy lens is broken up and removed using ultrasound waves or laser energy. Then, the folded IOL is inserted through the same incision and positioned in the correct place inside the eye. Once in place, the IOL unfolds and is secured into position.

There are several types of IOLs available, including monofocal, multifocal, toric, and accommodating lenses. Monofocal lenses provide clear vision at one distance, while multifocal lenses offer clear vision at multiple distances. Toric lenses correct astigmatism, and accommodating lenses can change shape to focus on objects at different distances.

Overall, intraocular lens implantation is a safe and effective procedure that can help restore clear vision in patients with cataracts or other eye conditions that require the removal of the natural lens.

Perceptual distortion is not explicitly defined within the realm of medicine, but it does fall under the broader category of cognitive impairments and abnormalities. It generally refers to the incorrect interpretation or misrepresentation of sensory information by the brain. This can result in various experiences such as hallucinations, illusions, or distorted perceptions of reality. Perceptual distortions are often associated with certain medical conditions like mental disorders (e.g., schizophrenia, bipolar disorder), neurological disorders (e.g., migraines, epilepsy), and substance use disorders.

Photorefractive Keratectomy (PRK) is a type of refractive surgery used to correct vision issues such as nearsightedness, farsightedness, and astigmatism. It works by reshaping the cornea using a laser, which alters how light enters the eye and focuses on the retina.

In PRK, the surgeon removes the thin outer layer of the cornea (epithelium) with an alcohol solution or a blunt surgical instrument before using the laser to reshape the underlying stromal layer. The epithelium then grows back during the healing process, which can take several days.

Compared to LASIK (another type of refractive surgery), PRK has a longer recovery time and may cause more discomfort in the first few days after surgery. However, it is an option for people who are not good candidates for LASIK due to thin corneas or other eye conditions.

It's important to note that while refractive surgeries like PRK can significantly improve vision and reduce dependence on glasses or contact lenses, they may not completely eliminate the need for corrective eyewear in all cases. Additionally, as with any surgical procedure, there are potential risks and complications associated with PRK, including infection, dry eye, and visual disturbances such as glare or halos around lights.

The Differential Threshold, also known as the Just Noticeable Difference (JND), is the minimum change in a stimulus that can be detected or perceived as different from another stimulus by an average human observer. It is a fundamental concept in psychophysics, which deals with the relationship between physical stimuli and the sensations and perceptions they produce.

The differential threshold is typically measured using methods such as the method of limits or the method of constant stimuli, in which the intensity of a stimulus is gradually increased or decreased until the observer can reliably detect a difference. The difference between the original stimulus and the barely detectable difference is then taken as the differential threshold.

The differential threshold can vary depending on a number of factors, including the type of stimulus (e.g., visual, auditory, tactile), the intensity of the original stimulus, the observer's attention and expectations, and individual differences in sensory sensitivity. Understanding the differential threshold is important for many applications, such as designing sensory aids for people with hearing or vision impairments, optimizing the design of multimedia systems, and developing more effective methods for detecting subtle changes in physiological signals.

Distance perception refers to the ability to accurately judge the distance or depth of an object in relation to oneself or other objects. It is a complex process that involves both visual and non-visual cues, such as perspective, size, texture, motion parallax, binocular disparity, and familiarity with the object or scene.

In the visual system, distance perception is primarily mediated by the convergence of the two eyes on an object, which provides information about its depth and location in three-dimensional space. The brain then integrates this information with other sensory inputs and prior knowledge to create a coherent perception of the environment.

Disorders of distance perception can result from various conditions that affect the visual system, such as amblyopia, strabismus, or traumatic brain injury. These disorders can cause difficulties in tasks that require accurate depth perception, such as driving, sports, or manual work.

Prospective studies, also known as longitudinal studies, are a type of cohort study in which data is collected forward in time, following a group of individuals who share a common characteristic or exposure over a period of time. The researchers clearly define the study population and exposure of interest at the beginning of the study and follow up with the participants to determine the outcomes that develop over time. This type of study design allows for the investigation of causal relationships between exposures and outcomes, as well as the identification of risk factors and the estimation of disease incidence rates. Prospective studies are particularly useful in epidemiology and medical research when studying diseases with long latency periods or rare outcomes.

Eye diseases are a range of conditions that affect the eye or visual system, causing damage to vision and, in some cases, leading to blindness. These diseases can be categorized into various types, including:

1. Refractive errors: These include myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia, which affect the way light is focused on the retina and can usually be corrected with glasses or contact lenses.
2. Cataracts: A clouding of the lens inside the eye that leads to blurry vision, glare, and decreased contrast sensitivity. Cataract surgery is the most common treatment for this condition.
3. Glaucoma: A group of diseases characterized by increased pressure in the eye, leading to damage to the optic nerve and potential blindness if left untreated. Treatment includes medications, laser therapy, or surgery.
4. Age-related macular degeneration (AMD): A progressive condition that affects the central part of the retina called the macula, causing blurry vision and, in advanced stages, loss of central vision. Treatment may include anti-VEGF injections, laser therapy, or nutritional supplements.
5. Diabetic retinopathy: A complication of diabetes that affects the blood vessels in the retina, leading to bleeding, leakage, and potential blindness if left untreated. Treatment includes laser therapy, anti-VEGF injections, or surgery.
6. Retinal detachment: A separation of the retina from its underlying tissue, which can lead to vision loss if not treated promptly with surgery.
7. Amblyopia (lazy eye): A condition where one eye does not develop normal vision, often due to a misalignment or refractive error in childhood. Treatment includes correcting the underlying problem and encouraging the use of the weaker eye through patching or other methods.
8. Strabismus (crossed eyes): A misalignment of the eyes that can lead to amblyopia if not treated promptly with surgery, glasses, or other methods.
9. Corneal diseases: Conditions that affect the transparent outer layer of the eye, such as keratoconus, Fuchs' dystrophy, and infectious keratitis, which can lead to vision loss if not treated promptly.
10. Uveitis: Inflammation of the middle layer of the eye, which can cause vision loss if not treated promptly with anti-inflammatory medications or surgery.

Reaction time, in the context of medicine and physiology, refers to the time period between the presentation of a stimulus and the subsequent initiation of a response. This complex process involves the central nervous system, particularly the brain, which perceives the stimulus, processes it, and then sends signals to the appropriate muscles or glands to react.

There are different types of reaction times, including simple reaction time (responding to a single, expected stimulus) and choice reaction time (choosing an appropriate response from multiple possibilities). These measures can be used in clinical settings to assess various aspects of neurological function, such as cognitive processing speed, motor control, and alertness.

However, it is important to note that reaction times can be influenced by several factors, including age, fatigue, attention, and the use of certain medications or substances.

"Melopsittacus" is the genus name for the species of bird commonly known as the Budgerigar or Parakeet. It is the only species in its genus and belongs to the Psittacidae family, which includes parrots. The Melopsittacus undulatus is a small, long-tailed parrot native to Australia, known for its bright green, yellow, or blue feathers and sociable behavior. They are popular pets due to their ease of care, playful personalities, and ability to mimic human speech.

Pseudophakia is a medical term that refers to the condition where a person's natural lens in the eye has been replaced with an artificial one. This procedure is typically performed during cataract surgery, where the cloudy, natural lens is removed and replaced with a clear, artificial lens to improve vision. The prefix "pseudo" means false or fake, and "phakia" refers to the natural lens of the eye, hence the term "Pseudophakia" implies a false or artificial lens.

Fluorescein angiography is a medical diagnostic procedure used in ophthalmology to examine the blood flow in the retina and choroid, which are the inner layers of the eye. This test involves injecting a fluorescent dye, Fluorescein, into a patient's arm vein. As the dye reaches the blood vessels in the eye, a specialized camera takes rapid sequences of photographs to capture the dye's circulation through the retina and choroid.

The images produced by fluorescein angiography can help doctors identify any damage to the blood vessels, leakage, or abnormal growth of new blood vessels. This information is crucial in diagnosing and managing various eye conditions such as age-related macular degeneration, diabetic retinopathy, retinal vein occlusions, and inflammatory eye diseases.

It's important to note that while fluorescein angiography is a valuable diagnostic tool, it does carry some risks, including temporary side effects like nausea, vomiting, or allergic reactions to the dye. In rare cases, severe adverse reactions can occur, so patients should discuss these potential risks with their healthcare provider before undergoing the procedure.

Miotics, also known as parasympathomimetics or cholinergic agents, are a class of medications that stimulate the parasympathetic nervous system. They work by activating muscarinic receptors, which are found in various organs throughout the body, including the eye. In the eye, miotics cause contraction of the circular muscle of the iris, resulting in pupillary constriction (miosis). This action can help to reduce intraocular pressure in patients with glaucoma.

Miotics may also have other effects on the eye, such as accommodation (focusing) and decreasing the production of aqueous humor. Some examples of miotics include pilocarpine, carbachol, and ecothiopate. It's important to note that the use of miotics can have side effects, including blurred vision, headache, and brow ache.

Radial Keratotomy (RK) is a type of refractive surgery used to correct vision problems such as nearsightedness and astigmatism. The procedure involves making small, precise incisions in the cornea in a radial pattern, like the spokes of a wheel. These incisions cause the cornea to change shape, which can help to improve the way that light is focused onto the retina and reduce the need for corrective lenses.

During the procedure, the surgeon uses a specialized blade or laser to make the incisions in the cornea. The incisions are typically made at the periphery of the cornea, leaving the central portion of the cornea untouched. This helps to preserve the strength and stability of the cornea while still allowing it to change shape enough to improve vision.

Radial keratotomy was first developed in the 1970s and was widely used in the 1980s and 1990s. However, it has largely been replaced by newer procedures such as LASIK and PRK, which are considered to be safer and more effective. RK is still occasionally performed in cases where other procedures are not an option or when a patient prefers this type of surgery.

It's important to note that any surgical procedure carries risks, including infection, scarring, and changes in vision. Patients considering radial keratotomy should discuss the potential benefits and risks with their eye care provider before making a decision.

Duane Retraction Syndrome (DRS) is a congenital eye movement disorder, characterized by limited abduction (lateral movement away from the nose) of the affected eye, and on attempted adduction (movement towards the nose), the eye retracts into the orbit and the lid narrows. It is often accompanied by other eye alignment or vision anomalies. The exact cause is not known, but it is believed to be a result of abnormal development of the cranial nerves that control eye movement during fetal development. DRS is usually idiopathic, but it can also be associated with other congenital anomalies. It is typically diagnosed in early childhood and managed with a combination of observation, prism glasses, and/or surgery, depending on the severity and impact on vision.

Retinitis pigmentosa (RP) is a group of rare, genetic disorders that involve a breakdown and loss of cells in the retina - a light-sensitive tissue located at the back of the eye. The retina converts light into electrical signals which are then sent to the brain and interpreted as visual images.

In RP, the cells that detect light (rods and cones) degenerate more slowly than other cells in the retina, leading to a progressive loss of vision. Symptoms typically begin in childhood with night blindness (difficulty seeing in low light), followed by a gradual narrowing of the visual field (tunnel vision). Over time, this can lead to significant vision loss and even blindness.

The condition is usually inherited and there are several different genes that have been associated with RP. The diagnosis is typically made based on a combination of genetic testing, family history, and clinical examination. Currently, there is no cure for RP, but researchers are actively working to develop new treatments that may help slow or stop the progression of the disease.

Neurological models are simplified representations or simulations of various aspects of the nervous system, including its structure, function, and processes. These models can be theoretical, computational, or physical and are used to understand, explain, and predict neurological phenomena. They may focus on specific neurological diseases, disorders, or functions, such as memory, learning, or movement. The goal of these models is to provide insights into the complex workings of the nervous system that cannot be easily observed or understood through direct examination alone.

A laser is not a medical term per se, but a physical concept that has important applications in medicine. The term "LASER" stands for "Light Amplification by Stimulated Emission of Radiation." It refers to a device that produces and amplifies light with specific characteristics, such as monochromaticity (single wavelength), coherence (all waves moving in the same direction), and high intensity.

In medicine, lasers are used for various therapeutic and diagnostic purposes, including surgery, dermatology, ophthalmology, and dentistry. They can be used to cut, coagulate, or vaporize tissues with great precision, minimizing damage to surrounding structures. Additionally, lasers can be used to detect and measure physiological parameters, such as blood flow and oxygen saturation.

It's important to note that while lasers are powerful tools in medicine, they must be used by trained professionals to ensure safe and effective treatment.

Psychometrics is a branch of psychology that deals with the theory and technique of psychological measurement, such as the development and standardization of tests used to measure intelligence, aptitude, personality, attitudes, and other mental abilities or traits. It involves the construction and validation of measurement instruments, including the determination of their reliability and validity, and the application of statistical methods to analyze test data and interpret results. The ultimate goal of psychometrics is to provide accurate, objective, and meaningful measurements that can be used to understand individual differences and make informed decisions in educational, clinical, and organizational settings.

Analysis of Variance (ANOVA) is a statistical technique used to compare the means of two or more groups and determine whether there are any significant differences between them. It is a way to analyze the variance in a dataset to determine whether the variability between groups is greater than the variability within groups, which can indicate that the groups are significantly different from one another.

ANOVA is based on the concept of partitioning the total variance in a dataset into two components: variance due to differences between group means (also known as "between-group variance") and variance due to differences within each group (also known as "within-group variance"). By comparing these two sources of variance, ANOVA can help researchers determine whether any observed differences between groups are statistically significant, or whether they could have occurred by chance.

ANOVA is a widely used technique in many areas of research, including biology, psychology, engineering, and business. It is often used to compare the means of two or more experimental groups, such as a treatment group and a control group, to determine whether the treatment had a significant effect. ANOVA can also be used to compare the means of different populations or subgroups within a population, to identify any differences that may exist between them.

The eye is the organ of sight, primarily responsible for detecting and focusing on visual stimuli. It is a complex structure composed of various parts that work together to enable vision. Here are some of the main components of the eye:

1. Cornea: The clear front part of the eye that refracts light entering the eye and protects the eye from harmful particles and microorganisms.
2. Iris: The colored part of the eye that controls the amount of light reaching the retina by adjusting the size of the pupil.
3. Pupil: The opening in the center of the iris that allows light to enter the eye.
4. Lens: A biconvex structure located behind the iris that further refracts light and focuses it onto the retina.
5. Retina: A layer of light-sensitive cells (rods and cones) at the back of the eye that convert light into electrical signals, which are then transmitted to the brain via the optic nerve.
6. Optic Nerve: The nerve that carries visual information from the retina to the brain.
7. Vitreous: A clear, gel-like substance that fills the space between the lens and the retina, providing structural support to the eye.
8. Conjunctiva: A thin, transparent membrane that covers the front of the eye and the inner surface of the eyelids.
9. Extraocular Muscles: Six muscles that control the movement of the eye, allowing for proper alignment and focus.

The eye is a remarkable organ that allows us to perceive and interact with our surroundings. Various medical specialties, such as ophthalmology and optometry, are dedicated to the diagnosis, treatment, and management of various eye conditions and diseases.

Esotropia is a type of ocular misalignment, also known as strabismus, in which one eye turns inward toward the nose. This condition can be constant or intermittent and may result in double vision or loss of depth perception. Esotropia is often classified based on its cause, age of onset, and frequency. Common forms include congenital esotropia, acquired esotropia, and accommodative esotropia. Treatment typically involves corrective eyewear, eye exercises, or surgery to realign the eyes.

Ocular hypertension is a medical condition characterized by elevated pressure within the eye (intraocular pressure or IOP), which is higher than normal but not necessarily high enough to cause any visible damage to the optic nerve or visual field loss. It serves as a significant risk factor for developing glaucoma, a sight-threatening disease.

The normal range of intraocular pressure is typically between 10-21 mmHg (millimeters of mercury). Ocular hypertension is often defined as an IOP consistently above 21 mmHg, although some studies suggest that even pressures between 22-30 mmHg may not cause damage in all individuals. Regular monitoring and follow-up with an ophthalmologist are essential for people diagnosed with ocular hypertension to ensure early detection and management of any potential glaucomatous changes. Treatment options include medications, laser therapy, or surgery to lower the IOP and reduce the risk of glaucoma onset.

In the context of medicine, "cues" generally refer to specific pieces of information or signals that can help healthcare professionals recognize and respond to a particular situation or condition. These cues can come in various forms, such as:

1. Physical examination findings: For example, a patient's abnormal heart rate or blood pressure reading during a physical exam may serve as a cue for the healthcare professional to investigate further.
2. Patient symptoms: A patient reporting chest pain, shortness of breath, or other concerning symptoms can act as a cue for a healthcare provider to consider potential diagnoses and develop an appropriate treatment plan.
3. Laboratory test results: Abnormal findings on laboratory tests, such as elevated blood glucose levels or abnormal liver function tests, may serve as cues for further evaluation and diagnosis.
4. Medical history information: A patient's medical history can provide valuable cues for healthcare professionals when assessing their current health status. For example, a history of smoking may increase the suspicion for chronic obstructive pulmonary disease (COPD) in a patient presenting with respiratory symptoms.
5. Behavioral or environmental cues: In some cases, behavioral or environmental factors can serve as cues for healthcare professionals to consider potential health risks. For instance, exposure to secondhand smoke or living in an area with high air pollution levels may increase the risk of developing respiratory conditions.

Overall, "cues" in a medical context are essential pieces of information that help healthcare professionals make informed decisions about patient care and treatment.

Optical coherence tomography (OCT) is a non-invasive imaging technique that uses low-coherence light to capture high-resolution cross-sectional images of biological tissues, particularly the retina and other ocular structures. OCT works by measuring the echo time delay of light scattered back from different depths within the tissue, creating a detailed map of the tissue's structure. This technique is widely used in ophthalmology to diagnose and monitor various eye conditions such as macular degeneration, diabetic retinopathy, and glaucoma.

Keratoconus is a degenerative non-inflammatory disorder of the eye, primarily affecting the cornea. It is characterized by a progressive thinning and steepening of the central or paracentral cornea, causing it to assume a conical shape. This results in irregular astigmatism, myopia, and scattering of light leading to blurred vision, visual distortions, and sensitivity to glare. The exact cause of keratoconus is unknown, but it may be associated with genetics, eye rubbing, and certain medical conditions. It typically starts in the teenage years and progresses into the third or fourth decade of life. Treatment options include glasses, contact lenses, cross-linking, and corneal transplantation in advanced cases.

Vigabatrin is an anticonvulsant medication used to treat certain types of seizures in adults and children. It works by reducing the abnormal excitement in the brain. The medical definition of Vigabatrin is: a irreversible inhibitor of GABA transaminase, which results in increased levels of gamma-aminobutyric acid (GABA) in the central nervous system. This medication is used as an adjunctive treatment for complex partial seizures and is available in oral form for administration.

It's important to note that Vigabatrin can cause serious side effects, including permanent vision loss, and its use should be closely monitored by a healthcare professional. It is also classified as a pregnancy category C medication, which means it may harm an unborn baby and should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus.

The macula lutea, often simply referred to as the macula or fovea centralis, is a part of the eye that is responsible for central vision and color perception. It's located in the center of the retina, the light-sensitive tissue at the back of the eye. The macula contains a high concentration of pigments called xanthophylls, which give it a yellowish color and protect the photoreceptor cells in this area from damage by blue light.

The central part of the macula is called the fovea, which is a small depression that contains only cones, the photoreceptor cells responsible for color vision and high visual acuity. The fovea is surrounded by the parafovea and the perifovea, which contain both cones and rods, the photoreceptor cells responsible for low-light vision and peripheral vision.

Damage to the macula can result in a loss of central vision and color perception, a condition known as age-related macular degeneration (AMD), which is a leading cause of blindness in older adults. Other conditions that can affect the macula include macular edema, macular holes, and macular pucker.

Intraocular pressure (IOP) is the fluid pressure within the eye, specifically within the anterior chamber, which is the space between the cornea and the iris. It is measured in millimeters of mercury (mmHg). The aqueous humor, a clear fluid that fills the anterior chamber, is constantly produced and drained, maintaining a balance that determines the IOP. Normal IOP ranges from 10-21 mmHg, with average values around 15-16 mmHg. Elevated IOP is a key risk factor for glaucoma, a group of eye conditions that can lead to optic nerve damage and vision loss if not treated promptly and effectively. Regular monitoring of IOP is essential in diagnosing and managing glaucoma and other ocular health issues.

Ocular dominance refers to the preference of one eye over the other in terms of visual perception and processing. In other words, it is the tendency for an individual to rely more heavily on the input from one particular eye when interpreting visual information. This can have implications in various visual tasks such as depth perception, aiming, and targeting.

Ocular dominance can be determined through a variety of tests, including the Miles test, the Porta test, or simply by observing which eye a person uses to align a visual target. It is important to note that ocular dominance does not necessarily indicate any sort of visual impairment or deficit; rather, it is a normal variation in the way that visual information is processed by the brain.

Hyperopia, also known as farsightedness, is a refractive error in which the eye does not focus light directly on the retina when looking at a distant object. Instead, light is focused behind the retina, causing close-up objects to appear blurry. This condition usually results from the eyeball being too short or the cornea having too little curvature. It can be corrected with eyeglasses, contact lenses, or refractive surgery.

I apologize, but "Alabama" is not a medical term or condition. It is the name of one of the states in the United States of America, located in the southeastern region. The term "Alabaman" is used to describe someone from this state. If you have any questions related to medical terminology or health concerns, I would be happy to help answer those for you.

Neurons, also known as nerve cells or neurocytes, are specialized cells that constitute the basic unit of the nervous system. They are responsible for receiving, processing, and transmitting information and signals within the body. Neurons have three main parts: the dendrites, the cell body (soma), and the axon. The dendrites receive signals from other neurons or sensory receptors, while the axon transmits these signals to other neurons, muscles, or glands. The junction between two neurons is called a synapse, where neurotransmitters are released to transmit the signal across the gap (synaptic cleft) to the next neuron. Neurons vary in size, shape, and structure depending on their function and location within the nervous system.

Eye movements, also known as ocular motility, refer to the voluntary or involuntary motion of the eyes that allows for visual exploration of our environment. There are several types of eye movements, including:

1. Saccades: rapid, ballistic movements that quickly shift the gaze from one point to another.
2. Pursuits: smooth, slow movements that allow the eyes to follow a moving object.
3. Vergences: coordinated movements of both eyes in opposite directions, usually in response to a three-dimensional stimulus.
4. Vestibulo-ocular reflex (VOR): automatic eye movements that help stabilize the gaze during head movement.
5. Optokinetic nystagmus (OKN): rhythmic eye movements that occur in response to large moving visual patterns, such as when looking out of a moving vehicle.

Abnormalities in eye movements can indicate neurological or ophthalmological disorders and are often assessed during clinical examinations.

"Age factors" refer to the effects, changes, or differences that age can have on various aspects of health, disease, and medical care. These factors can encompass a wide range of issues, including:

1. Physiological changes: As people age, their bodies undergo numerous physical changes that can affect how they respond to medications, illnesses, and medical procedures. For example, older adults may be more sensitive to certain drugs or have weaker immune systems, making them more susceptible to infections.
2. Chronic conditions: Age is a significant risk factor for many chronic diseases, such as heart disease, diabetes, cancer, and arthritis. As a result, age-related medical issues are common and can impact treatment decisions and outcomes.
3. Cognitive decline: Aging can also lead to cognitive changes, including memory loss and decreased decision-making abilities. These changes can affect a person's ability to understand and comply with medical instructions, leading to potential complications in their care.
4. Functional limitations: Older adults may experience physical limitations that impact their mobility, strength, and balance, increasing the risk of falls and other injuries. These limitations can also make it more challenging for them to perform daily activities, such as bathing, dressing, or cooking.
5. Social determinants: Age-related factors, such as social isolation, poverty, and lack of access to transportation, can impact a person's ability to obtain necessary medical care and affect their overall health outcomes.

Understanding age factors is critical for healthcare providers to deliver high-quality, patient-centered care that addresses the unique needs and challenges of older adults. By taking these factors into account, healthcare providers can develop personalized treatment plans that consider a person's age, physical condition, cognitive abilities, and social circumstances.

Macular edema is a medical condition characterized by the accumulation of fluid in the macula, a small area in the center of the retina responsible for sharp, detailed vision. This buildup of fluid causes the macula to thicken and swell, which can distort central vision and lead to vision loss if not treated promptly. Macular edema is often a complication of other eye conditions such as diabetic retinopathy, age-related macular degeneration, retinal vein occlusion, or uveitis. It's important to note that while macular edema can affect anyone, it is more common in people with certain medical conditions like diabetes.

The optic nerve, also known as the second cranial nerve, is the nerve that transmits visual information from the retina to the brain. It is composed of approximately one million nerve fibers that carry signals related to vision, such as light intensity and color, from the eye's photoreceptor cells (rods and cones) to the visual cortex in the brain. The optic nerve is responsible for carrying this visual information so that it can be processed and interpreted by the brain, allowing us to see and perceive our surroundings. Damage to the optic nerve can result in vision loss or impairment.

Child development is a multidisciplinary field that examines the biological, psychological, emotional, and social growth and changes that occur in human beings between birth and the onset of adulthood. It involves a complex interaction of genetics, environment, culture, and experiences that shape a child's growth and development over time.

Child development is typically divided into several domains, including:

1. Physical Development: This refers to the growth and changes in a child's body, including their motor skills, sensory abilities, and overall health.
2. Cognitive Development: This involves the development of a child's thinking, learning, problem-solving, memory, language, and other mental processes.
3. Emotional Development: This refers to the development of a child's emotional awareness, expression, understanding, and regulation.
4. Social Development: This involves the development of a child's ability to interact with others, form relationships, communicate effectively, and understand social norms and expectations.

Child development is an ongoing process that occurs at different rates and in different ways for each child. Understanding typical patterns of child development can help parents, educators, and healthcare providers support children's growth and identify any potential delays or concerns.

The crystalline lens is a biconvex transparent structure in the eye that helps to refract (bend) light rays and focus them onto the retina. It is located behind the iris and pupil and is suspended by small fibers called zonules that connect it to the ciliary body. The lens can change its shape to accommodate and focus on objects at different distances, a process known as accommodation. With age, the lens may become cloudy or opaque, leading to cataracts.

The cornea is the clear, dome-shaped surface at the front of the eye. It plays a crucial role in focusing vision. The cornea protects the eye from harmful particles and microorganisms, and it also serves as a barrier against UV light. Its transparency allows light to pass through and get focused onto the retina. The cornea does not contain blood vessels, so it relies on tears and the fluid inside the eye (aqueous humor) for nutrition and oxygen. Any damage or disease that affects its clarity and shape can significantly impact vision and potentially lead to blindness if left untreated.

Photoreceptor cells are specialized neurons in the retina of the eye that convert light into electrical signals. These cells consist of two types: rods and cones. Rods are responsible for vision at low light levels and provide black-and-white, peripheral, and motion sensitivity. Cones are active at higher light levels and are capable of color discrimination and fine detail vision. Both types of photoreceptor cells contain light-sensitive pigments that undergo chemical changes when exposed to light, triggering a series of electrical signals that ultimately reach the brain and contribute to visual perception.

Retinal vessels refer to the blood vessels that are located in the retina, which is the light-sensitive tissue that lines the inner surface of the eye. The retina contains two types of blood vessels: arteries and veins.

The central retinal artery supplies oxygenated blood to the inner layers of the retina, while the central retinal vein drains deoxygenated blood from the retina. These vessels can be visualized during a routine eye examination using an ophthalmoscope, which allows healthcare professionals to assess their health and any potential abnormalities.

Retinal vessels are essential for maintaining the health and function of the retina, and any damage or changes to these vessels can affect vision and lead to various eye conditions such as diabetic retinopathy, retinal vein occlusion, and hypertensive retinopathy.

Diagnostic techniques in ophthalmology refer to the various methods and tests used by eye specialists (ophthalmologists) to examine, evaluate, and diagnose conditions related to the eyes and visual system. Here are some commonly used diagnostic techniques:

1. Visual Acuity Testing: This is a basic test to measure the sharpness of a person's vision. It typically involves reading letters or numbers from an eye chart at a specific distance.
2. Refraction Test: This test helps determine the correct lens prescription for glasses or contact lenses by measuring how light is bent as it passes through the cornea and lens.
3. Slit Lamp Examination: A slit lamp is a microscope that allows an ophthalmologist to examine the structures of the eye, including the cornea, iris, lens, and retina, in great detail.
4. Tonometry: This test measures the pressure inside the eye (intraocular pressure) to detect conditions like glaucoma. Common methods include applanation tonometry and non-contact tonometry.
5. Retinal Imaging: Several techniques are used to capture images of the retina, including fundus photography, fluorescein angiography, and optical coherence tomography (OCT). These tests help diagnose conditions like macular degeneration, diabetic retinopathy, and retinal detachments.
6. Color Vision Testing: This test evaluates a person's ability to distinguish between different colors, which can help detect color vision deficiencies or neurological disorders affecting the visual pathway.
7. Visual Field Testing: This test measures a person's peripheral (or side) vision and can help diagnose conditions like glaucoma, optic nerve damage, or brain injuries.
8. Pupillary Reactions Tests: These tests evaluate how the pupils respond to light and near objects, which can provide information about the condition of the eye's internal structures and the nervous system.
9. Ocular Motility Testing: This test assesses eye movements and alignment, helping diagnose conditions like strabismus (crossed eyes) or nystagmus (involuntary eye movement).
10. Corneal Topography: This non-invasive imaging technique maps the curvature of the cornea, which can help detect irregularities, assess the fit of contact lenses, and plan refractive surgery procedures.

I'm sorry for any confusion, but "Macaca" is not a medical term. It is the name of a genus that includes several species of monkeys, commonly known as macaques. These primates are often used in biomedical research due to their similarities with humans in terms of genetics and physiology. If you have any questions related to medicine or health, I would be happy to try to help answer them.

In the context of medicine, particularly in anatomy and physiology, "rotation" refers to the movement of a body part around its own axis or the long axis of another structure. This type of motion is three-dimensional and can occur in various planes. A common example of rotation is the movement of the forearm bones (radius and ulna) around each other during pronation and supination, which allows the hand to be turned palm up or down. Another example is the rotation of the head during mastication (chewing), where the mandible moves in a circular motion around the temporomandibular joint.

In psychology, Signal Detection Theory (SDT) is a framework used to understand the ability to detect the presence or absence of a signal (such as a stimulus or event) in the presence of noise or uncertainty. It is often applied in sensory perception research, such as hearing and vision, where it helps to separate an observer's sensitivity to the signal from their response bias.

SDT involves measuring both hits (correct detections of the signal) and false alarms (incorrect detections when no signal is present). These measures are then used to calculate measures such as d', which reflects the observer's ability to discriminate between the signal and noise, and criterion (C), which reflects the observer's response bias.

SDT has been applied in various fields of psychology, including cognitive psychology, clinical psychology, and neuroscience, to study decision-making, memory, attention, and perception. It is a valuable tool for understanding how people make decisions under uncertainty and how they trade off accuracy and caution in their responses.

"Macaca mulatta" is the scientific name for the Rhesus macaque, a species of monkey that is native to South, Central, and Southeast Asia. They are often used in biomedical research due to their genetic similarity to humans.

A case-control study is an observational research design used to identify risk factors or causes of a disease or health outcome. In this type of study, individuals with the disease or condition (cases) are compared with similar individuals who do not have the disease or condition (controls). The exposure history or other characteristics of interest are then compared between the two groups to determine if there is an association between the exposure and the disease.

Case-control studies are often used when it is not feasible or ethical to conduct a randomized controlled trial, as they can provide valuable insights into potential causes of diseases or health outcomes in a relatively short period of time and at a lower cost than other study designs. However, because case-control studies rely on retrospective data collection, they are subject to biases such as recall bias and selection bias, which can affect the validity of the results. Therefore, it is important to carefully design and conduct case-control studies to minimize these potential sources of bias.

Laser coagulation, also known as laser photocoagulation, is a medical procedure that uses a laser to seal or destroy abnormal blood vessels or tissue. The laser produces a concentrated beam of light that can be precisely focused on the target area. When the laser energy is absorbed by the tissue, it causes the temperature to rise, which leads to coagulation (the formation of a clot) or destruction of the tissue.

In ophthalmology, laser coagulation is commonly used to treat conditions such as diabetic retinopathy, age-related macular degeneration, and retinal tears or holes. The procedure can help to seal leaking blood vessels, reduce fluid leakage, and prevent further vision loss. It is usually performed as an outpatient procedure and may be repeated if necessary.

In other medical specialties, laser coagulation may be used to control bleeding, destroy tumors, or remove unwanted tissue. The specific technique and parameters of the laser treatment will depend on the individual patient's needs and the condition being treated.

Choroidal neovascularization (CNV) is a medical term that refers to the growth of new, abnormal blood vessels in the choroid layer of the eye, which is located between the retina and the sclera. This condition typically occurs as a complication of age-related macular degeneration (AMD), although it can also be caused by other eye diseases or injuries.

In CNV, the new blood vessels that grow into the choroid layer are fragile and can leak fluid or blood, which can cause distortion or damage to the retina, leading to vision loss. Symptoms of CNV may include blurred or distorted vision, a blind spot in the center of the visual field, or changes in color perception.

Treatment for CNV typically involves medications that are designed to stop the growth of new blood vessels, such as anti-VEGF drugs, which target a protein called vascular endothelial growth factor (VEGF) that is involved in the development of new blood vessels. Laser surgery or photodynamic therapy may also be used in some cases to destroy the abnormal blood vessels and prevent further vision loss.

Radiation scattering is a physical process in which radiation particles or waves deviate from their original direction due to interaction with matter. This phenomenon can occur through various mechanisms such as:

1. Elastic Scattering: Also known as Thomson scattering or Rayleigh scattering, it occurs when the energy of the scattered particle or wave remains unchanged after the collision. In the case of electromagnetic radiation (e.g., light), this results in a change of direction without any loss of energy.
2. Inelastic Scattering: This type of scattering involves an exchange of energy between the scattered particle and the target medium, leading to a change in both direction and energy of the scattered particle or wave. An example is Compton scattering, where high-energy photons (e.g., X-rays or gamma rays) interact with charged particles (usually electrons), resulting in a decrease in photon energy and an increase in electron kinetic energy.
3. Coherent Scattering: In this process, the scattered radiation maintains its phase relationship with the incident radiation, leading to constructive and destructive interference patterns. An example is Bragg scattering, which occurs when X-rays interact with a crystal lattice, resulting in diffraction patterns that reveal information about the crystal structure.

In medical contexts, radiation scattering can have both beneficial and harmful effects. For instance, in diagnostic imaging techniques like computed tomography (CT) scans, radiation scattering contributes to image noise and reduces contrast resolution. However, in radiation therapy for cancer treatment, controlled scattering of therapeutic radiation beams can help ensure that the tumor receives a uniform dose while minimizing exposure to healthy tissues.

Psychomotor performance refers to the integration and coordination of mental processes (cognitive functions) with physical movements. It involves the ability to perform complex tasks that require both cognitive skills, such as thinking, remembering, and perceiving, and motor skills, such as gross and fine motor movements. Examples of psychomotor performances include driving a car, playing a musical instrument, or performing surgical procedures.

In a medical context, psychomotor performance is often used to assess an individual's ability to perform activities of daily living (ADLs) and instrumental activities of daily living (IADLs), such as bathing, dressing, cooking, cleaning, and managing medications. Deficits in psychomotor performance can be a sign of neurological or psychiatric disorders, such as dementia, Parkinson's disease, or depression.

Assessment of psychomotor performance may involve tests that measure reaction time, coordination, speed, precision, and accuracy of movements, as well as cognitive functions such as attention, memory, and problem-solving skills. These assessments can help healthcare professionals develop appropriate treatment plans and monitor the progression of diseases or the effectiveness of interventions.

Computer-assisted diagnosis (CAD) is the use of computer systems to aid in the diagnostic process. It involves the use of advanced algorithms and data analysis techniques to analyze medical images, laboratory results, and other patient data to help healthcare professionals make more accurate and timely diagnoses. CAD systems can help identify patterns and anomalies that may be difficult for humans to detect, and they can provide second opinions and flag potential errors or uncertainties in the diagnostic process.

CAD systems are often used in conjunction with traditional diagnostic methods, such as physical examinations and patient interviews, to provide a more comprehensive assessment of a patient's health. They are commonly used in radiology, pathology, cardiology, and other medical specialties where imaging or laboratory tests play a key role in the diagnostic process.

While CAD systems can be very helpful in the diagnostic process, they are not infallible and should always be used as a tool to support, rather than replace, the expertise of trained healthcare professionals. It's important for medical professionals to use their clinical judgment and experience when interpreting CAD results and making final diagnoses.

An action potential is a brief electrical signal that travels along the membrane of a nerve cell (neuron) or muscle cell. It is initiated by a rapid, localized change in the permeability of the cell membrane to specific ions, such as sodium and potassium, resulting in a rapid influx of sodium ions and a subsequent efflux of potassium ions. This ion movement causes a brief reversal of the electrical potential across the membrane, which is known as depolarization. The action potential then propagates along the cell membrane as a wave, allowing the electrical signal to be transmitted over long distances within the body. Action potentials play a crucial role in the communication and functioning of the nervous system and muscle tissue.

Follow-up studies are a type of longitudinal research that involve repeated observations or measurements of the same variables over a period of time, in order to understand their long-term effects or outcomes. In medical context, follow-up studies are often used to evaluate the safety and efficacy of medical treatments, interventions, or procedures.

In a typical follow-up study, a group of individuals (called a cohort) who have received a particular treatment or intervention are identified and then followed over time through periodic assessments or data collection. The data collected may include information on clinical outcomes, adverse events, changes in symptoms or functional status, and other relevant measures.

The results of follow-up studies can provide important insights into the long-term benefits and risks of medical interventions, as well as help to identify factors that may influence treatment effectiveness or patient outcomes. However, it is important to note that follow-up studies can be subject to various biases and limitations, such as loss to follow-up, recall bias, and changes in clinical practice over time, which must be carefully considered when interpreting the results.

The postoperative period is the time following a surgical procedure during which the patient's response to the surgery and anesthesia is monitored, and any complications or adverse effects are managed. This period can vary in length depending on the type of surgery and the individual patient's needs, but it typically includes the immediate recovery phase in the post-anesthesia care unit (PACU) or recovery room, as well as any additional time spent in the hospital for monitoring and management of pain, wound healing, and other aspects of postoperative care.

The goals of postoperative care are to ensure the patient's safety and comfort, promote optimal healing and rehabilitation, and minimize the risk of complications such as infection, bleeding, or other postoperative issues. The specific interventions and treatments provided during this period will depend on a variety of factors, including the type and extent of surgery performed, the patient's overall health and medical history, and any individualized care plans developed in consultation with the patient and their healthcare team.

This test uses a series of cards depicting cartoon faces of different contrast levels. The contrast sensitivity assessment ... It is especially vital to assess a child's contrast sensitivity at a young age in order to determine the distance and accuracy ... such as contrast sensitivity, visual field, color vision, visual adaptation, motion perception, and ocular function and ... Contrast sensitivity. Retrieved from Official website ( ...
... which is the ratio of binocular contrast sensitivity to the contrast sensitivity of the better eye. B S R = C S b i n o c u l a ... Contrast sensitivity. Visual acuity. A practical measure of binocularity is the binocular summation ratio BSR, ... By combining the information received in each eye, binocular summation can improve visual acuity, contrast sensitivity, flicker ... Schrödinger (1926) put forth an equation for binocular brightness and contrast combination where each monocular input is ...
"Contrast sensitivity" (PDF). LEA-Test Ltd. Retrieved 21 July 2018. Physiologic Optics: Dioptrics of the Eye, Functions of the ... This produces a contrast of about 1% with the illumination of surrounding cones. The mechanism of detection is the ability to ... In low light (i.e., scotopic vision), cones do not have sufficient sensitivity and vision is subserved by rods. Spatial ... Under optimal conditions of good illumination, high contrast, and long line segments, the limit to vernier acuity is about 8 ...
A person's contrast sensitivity function is contrast sensitivity as a function of spatial frequency. Normally, peak contrast ... Contrast sensitivity is the reciprocal of the smallest contrast for which a person can see a sine-wave grating. ... Reducing the contrast of an image reduces the visibility of these high spatial frequencies because contrast sensitivity for ... The ability of a person with normal visual acuity to see fine details is determined by contrast sensitivity. ...
ISBN 0-471-97440-4. Peter G. J. Barten (1999). Contrast Sensitivity of the Human Eye and Its Effects on Image Quality. SPIE ... A database of camera spectral sensitivity is created and its space analyzed. For X-ray films, the spectral sensitivity is ... incorporating the spectral sensitivity. When the sensor system is linear, its spectral sensitivity and spectral responsivity ... Spectral sensitivity is the relative efficiency of detection, of light or other signal, as a function of the frequency or ...
Contrast sensitivity may be affected. The change in the refractive index of the cornea may result in subtle refractive shifts, ...
Contrast sensitivity may be diminished. There could be an abnormal electroretinogram or visual evoked potentials. Neuron- ...
2 Visual Acuity, Contrast Sensitivity". University of Utah. Retrieved 19 July 2009. (Articles with short description, Short ... such as contrast sensitivity. In these stimuli, spatial frequency is expressed as the number of cycles per degree of visual ... Barghout, Lauren (2014). Vision: How Global Perceptual Context Changes Local Contrast ...
Contrast sensitivity is the inverse of the smallest contrast that can be detected; a contrast sensitivity of 100 means that the ... A contrast sensitivity function describes an animal's ability to detect the contrast of grating patterns of different spatial ... Birds have comparably lower contrast sensitivity than mammals. Humans have been shown to detect contrasts as low as 0.5-1% ... Spatial luminance contrast sensitivity tests of macaque and human observers". Vision Research. 14 (1): 75-81. doi:10.1016/0042- ...
Do you have a low-contrast sensitivity? For example, do they have trouble seeing a grey car at dusk, a black car at night, or a ...
... and the sensitivity to contrast in sine wave stimuli is characterized by the contrast sensitivity function. Contrast ... Skottun, Bernt C.; Skoyles, John R. (2007). "Contrast sensitivity and magnocellular functioning in schizophrenia". Vision ... "Spatio-temporal luminance contrast sensitivity and visual backward masking in schizophrenia". Experimental Brain Research. 156 ... "The effect of peripheral visual motion on focal contrast sensitivity in positive-and negative-symptom schizophrenia". ...
Harper L, Spencer E, Davidson C, Hutchinson CV (January 2020). "Selectively reduced contrast sensitivity in high schizotypy". ... In addition, people with StPD can have decreased capacities for multisensory integration or contrast sensitivity, either ... Kent BW, Weinstein ZA, Passarelli V, Chen Y, Siever LJ (April 2011). "Deficient visual sensitivity in schizotypal personality ...
"Luminance Contrast". Hwang, Alex D; Peli, Eli (14 February 2016). "Positive and negative polarity contrast sensitivity ... brightness contrast, lightness contrast, color contrast, simultaneous contrast, successive contrast, etc.). Contrast in physics ... The contrast between two full-screen patterns (full-screen contrast) always is a successive contrast.[citation needed] contrast ... 1 means no contrast. The contrast can also be specified by the contrast modulation (or Michelson contrast), CM, defined as: C M ...
Norcia and Tyler have used the technique to document the development of visual acuity and contrast sensitivity through the ... Norcia A. M.; Tyler C. W.; Allen D. (1986). "Electrophysiological assessment of contrast sensitivity in human infants". ... The resulting plot of stimulus luminance versus wavelength is a plot of the spectral sensitivity of the visual system. Sensory ...
Niemeyer, James E.; Paradiso, Michael A. (2017-02-01). "Contrast sensitivity, V1 neural activity, and natural vision". Journal ... The fading of the lilac circles is due to a loss of sensitivity to that stimulus and the adaptation to the new stimulus. To ... Visual adaptation is the temporary change in sensitivity or perception when exposed to a new or intense stimulus, and the ... The aftereffects of exposure to a visual stimulus or pattern causes loss of sensitivity to that pattern and induces stimulus ...
Most older adult humans lose photopic spatial contrast sensitivity. Adults in their 70s tend to require about 30-60% more ... "Aging and Neural Spatial Contrast Sensitivity: Photopic Vision". Vision Research. 33 (7): 939-949. doi:10.1016/0042-6989(93) ... Their sensitivity ranges overlap to provide vision throughout the visible spectrum. The maximum efficacy is 683 lm/W at a ... Candela Cone cell Contrast (vision) Mesopic vision Night vision Purkinje effect Photometry (optics) Photosensitive ganglion ...
The NHK measured contrast sensitivity for the Rec. 2020 color space using Barten's equation which had previously been used to ...
Colored transparent insert discs to increase the contrast sensitivity. Semi-transparent occluder to block the non-aiming eye ... In contrast to most other eye glasses, shooting glasses usually only have one lens that corrects the ametropia of the dominant ...
Nityananda, V.; Tarawneh, G.; Jones, L.; Busby, N.; Herbert, W.; Davies, R.; Read, J. C. A. (2015). "The contrast sensitivity ...
It was a stark contrast to his own heightened sensitivity. During this time in prison he began experiencing the epileptic ...
C. Enroth-Cugell; J. G. Robson (1966). "The Contrast Sensitivity of Retinal Ganglion Cells of the Cat". Journal of Physiology. ... A major drawback to application of the algorithm is an inherent reduction in overall image contrast produced by the operation. ... Marr and Hildreth recommend the ratio of 1.6 because of design considerations balancing bandwidth and sensitivity. The url for ...
These improvement theories include the improvement of visual contrast sensitivity. Other developments include the ability to ...
Enroth-Cugell C, Robson JG (December 1966). "The contrast sensitivity of retinal ganglion cells of the cat". The Journal of ...
... may rarely cause a reduction in best night-time acuity due to the impairment of contrast sensitivity function (CSF) which is ... "Laser in situ keratomileusis for myopia and the contrast sensitivity function". Journal of Cataract and Refractive Surgery. 30 ... Contrast vision may also be greatly reduced. Rods contain a receptor-protein called rhodopsin. When light falls on rhodopsin, ...
Recordings of S potentials at the axon terminals of RGCs in the LGN suggest that there is high contrast sensitivity in the ... opposed by low contrast sensitivity in cells found in the parvocellular layer. Both old and new world primates have been used ... Due to this contrast information, these cells are good at detecting changes in luminance, and thus provide useful information ... Parasol ganglion cells have high light/dark contrast detection, and are more sensitive at low spatial frequencies than high ...
Spatial luminance contrast sensitivity tests of macaque and human observers", Vision Res. 14: 75-81 (1974). Thorell, L.G., De ... Spatial luminance contrast sensitivity tests of macaque and human observers", Vision Res. 14: 75-81 (1974) De Valois, R.L. & ... That the wavelength discrimination and luminance contrast sensitivity measured in monkeys were very similar to those obtained ... had proposed that the percept of color emerged from spectrally-opponent mechanisms in the visual system that contrasted red vs ...
This contrasted with the left hemisphere's lower level of sensitivity to variations. Although the concept of the left-brain ... In fMRI studies by Koutstaal the level of sensitivity of the right visual cortex with respect to the single exposure of an ... These studies illustrate the role of the left prefrontal cortex in exerting control over one's environment in contrast to the ...
Optical filter systems to increase the contrast sensitivity for the aiming eye. Semi-transparent occluders for the non-aiming ...
In contrast, sensitivity is expected to be lowest for individuals with childhood environments that were neither extremely ... Environmental Sensitivity proposes that sensitivity is driven primarily by a heightened sensitivity of the central nervous ... Sensory processing sensitivity (SPS) theory by Elaine N. Aron and Arthur Aron proposes that sensitivity is a stable human trait ... Given that sensitivity is a complex trait, similar to other personality dimensions, it is more helpful to measure sensitivity ...
The physiognomy and the surface of the sitter's skin are delicately rendered; delicacy and sensitivity contrast with the long, ...
Contrast sensitivity -- RDoC Element. Type of Element: Paradigm. The following construct(s)/subconstruct(s) refer to this ... Home , Research , Research Funded by NIMH , Research Domain Criteria (RDoC) , Units of Analysis , Paradigms , Contrast ...
The contrast sensitivity function (CSF) is routinely assessed in clinical evaluation of vision and is the primary limiting ... We found that the very act of action video game playing also enhanced contrast sensitivity, providing a complementary route to ... This study finds that playing an action video game results in improvements in visual contrast sensitivity. These improvements ... Li, R., Polat, U., Makous, W. et al. Enhancing the contrast sensitivity function through action video game training. Nat ...
Gary Heiting describes how a contrast sensitivity test can detect vision problems that might not show up on a conventional eye ... How contrast sensitivity testing is done. Contrast sensitivity testing often isn't included in a routine eye test. Your ... What is a contrast sensitivity test?. A contrast sensitivity test measures your ability to distinguish between finer and finer ... Symptoms of reduced contrast sensitivity. If you have low contrast sensitivity, you may have problems with night driving, ...
Learn about the autoencoders and the relevance of low-level vision tasks of the contrast sensitivity functions using artificial ... For a study, researchers reconsidered the role of low-level vision tasks in explaining contrast sensitivity functions (CSFs) in ... proposed three decades ago that human frequency sensitivity may derive from the augmentation necessary for more effective ... of the maximal sensitivity. As a second contribution, they presented experimental evidence that deeper CNNs better at ...
To obtain measures of contrast sensitivity and threshold. *To determine the effects of haze glasses on visual acuity and ... Prior to assessing contrast sensitivity (CS) determine distance vision/visual acuity using the Snellen chart. ... The tester records the results to produce a contrast sensitivity function (CSF) or curve. ... Within each triplet all letters have the same contrast. The contrast decreases from one triplet to the next. The chart should ...
A new study published in Vision Research has highlighted that contrast sensitivity can be enhanced by light in a specific ... The scientists found that contrast sensitivity was enhanced when the amount of stimulation of melanopsin cells increased by ... Specific light spectrum improves contrast sensitivity. Experiments by researchers found visual acuity improved when viewers ... Specific spectrum of light enhances contrast sensitivity ...
The physical model for the spatial contrast sensitivity of the eye that we presented in a previous paper is extended to the ... Spatiotemporal model for the contrast sensitivity of the human eye and its temporal aspects Author(s): Peter G. J. Barten ... Spatio-temporal and temporal contrast sensitivity curves calculated with the model are compared with measurements published in ...
Contrast sensitivity is similarly reduced in Drd4−/−, Npas2−/−, and Adcy1−/− mice. Contrast sensitivity of Drd4−/− mice was ... Contrast sensitivity testing began with grating of 100% contrast and was gradually reduced until the contrast threshold was ... 3C; p , 0.001). Daytime contrast sensitivity in the LD cycle was significantly reduced, while night-time contrast sensitivity ... 3B; p , 0.001). Daytime contrast sensitivity measurements were significantly reduced while night-time contrast sensitivity was ...
... but could be detected by contrast sensitivity and glare testing. Dr. Pinakin Davey of Western University School of Health ... Contrast Sensitivity Detects Vision Problem in Genetic Disorder * CSV-1000 Shows Tinted Lenses Improve Vision for Diabetic ... He therefore conducted another study where he evaluated both contrast sensitivity and glare. His results showed a significant, ... Contrast Sensitivity Detects Vision Problem in Genetic Disorder. Posted on June 16, 2016 ...
Axial length, Bird vision, Contrast sensitivity, Corneal diameter, Optocollic, Phylogeny. in The Journal of experimental ... Low achromatic contrast sensitivity in birds : a common attribute shared by many phylogenetic orders. *Mark ... However, sensitivity to achromatic contrasts - the ability to discern luminance difference between two objects or an object and ... However, sensitivity to achromatic contrasts - the ability to discern luminance difference between two objects or an object and ...
It shares with optical imaging, that it uses non-ionizing radiation and provides higher contrast and higher sensitivity than ... We have discovered that, the amplitude of the photoacoustic signal generated from nano-contrast agents depends not only on the ... However, the molecular probes used for most of these studies were contrast agents simply adopted from other optical imaging ... Our research on photoacoustic contrast agents indicated that the mechanism of photoacoustic signal generation from nanometer- ...
Single shot x-ray phase contrast imaging using a direct conversion microstrip detector with single photon sensitivity ... Single shot x-ray phase contrast imaging using a direct conversion microstrip detector with single photon sensitivity. Applied ...
Contrast sensitivity and appearance in briefly presented illusory figures ... Contrast sensitivity and appearance in briefly presented illusory figures Rieger, J., & Gegenfurtner, K. (1999). Contrast ... illusory figure formation and figural completion to changes in contrast sensitivity in contour gaps. The brightness on the ... We found that contrast thresholds were lower than in a control condition without inducers, and that the threshold reduction was ...
Contrast Sensitivity. cpd. cycles per degree. PCLA. percentage of contrast left eye line A (line A represents 1.5 cpd). ... percentage of contrast right eye line A (line A represents 1.5 cpd). ... percentage of contrast left eye line B (line B represents 3.0 cpd). ... percentage of contrast right eye line B (line B represents 3.0 cpd). ...
title = "Measuring contrast sensitivity",. abstract = "Contrast sensitivity defines the threshold between the visible and ... Measuring contrast sensitivity. / Pelli, Denis G.; Bex, Peter. In: Vision research, Vol. 90, 09.2013, p. 10-14.. Research ... Pelli DG, Bex P. Measuring contrast sensitivity. Vision research. 2013 Sep;90:10-14. doi: 10.1016/j.visres.2013.04.015 ... N2 - Contrast sensitivity defines the threshold between the visible and invisible, which has obvious significance for basic and ...
... Abstract:. Contrast sensitivity is one of the components of visual function, ... We present theoretical and practical aspects related to the evolution of contrast sensitivity before and after laser ...
Visual Contrast Sensitivity. On-line free medical diagnosis assistant. Ranked list of possible diseases from either several ... Contrast sensitivity (Visual Contrast Sensitivity). The ability to detect sharp boundaries (stimuli) and to detect slight ...
GADELHA, Maria José Nunes et al. Achromatic contrast sensitivity for vertical sine-wave gratings in adolescents and adults. ... The aim of this study was to characterize the contrast sensitivity function (CSF) of adolescents and young adults. Was measured ... Keywords : Visual perception; Contrast sensitivity; Psychophysical method; Linear sine-wave grating; Adolescents and adults. ... These results suggest that the process of development and maturation of the visual perception of contrast interacts differently ...
2.1.2 Contrast Sensitivity. Contrast can be defined as the difference between the luminance of a region and its background. The ... Contrast-sensitivity mechanisms of human vision also determine which compression or processing artifacts we see and which we ... Since the human eye has reduced contrast sensitivity at higher frequencies, the same pattern is more difficult to see from a ... This effect can be modeled by tracking eye movements of the viewer and motion compensating the contrast sensitivity function ...
colour.CONTRAST_SENSITIVITY_METHODS#. colour.CONTRAST_SENSITIVITY_METHODS = CanonicalMapping({Barten 1999: ...})#. Supported ... Contrast Sensitivity. *colour.contrast_sensitivity_function. *colour.CONTRAST_SENSITIVITY_METHODS. *colour.contrast.contrast_ ...
... .ad-below-title-above-image { width: 320px; height: 100px; } @media(min- ... following test is based on tests issued by eye doctors in order to test a patients ability to recognize changes in contrast. ...
Improvement of contrast sensitivity. On a bright, sunny day, irradiance from the sun ranges from 10,000-30,000 foot-lamberts. ... These high light levels tend to saturate the retina and therefore decrease finer levels of contrast sensitivity. The major ... Reduction of glare sensitivity. Various types of sunglasses can reduce glare sensitivity. Because light reflected off a ... sunglasses is to allow the retina to remain at its normal level of contrast sensitivity. Most dark sunglasses absorb 70%-80% of ...
Please review the images and text below to learn about the various contrast sensitivity test faces that can be used with the ... Please visit this page for background information describing the basics of contrast sensitivity. ... Contrast sensitivity testing is accomplished worldwide by eye doctors in more than 60 countries using the CSV-1000 instrument. ... Contrast Sensitivity, Low Contrast, Low Contrast & Low Vision Charts, Near Vision Charts, Pediatric Opthalmology. Mayer-Kran™ ...
Key Variables For Contrast Sensitivity. Posted on October 3, 2020 There are a number of variables that contribute to improved ... 4. FACTOR: PIXEL PITCH- The Pixel Pitch has an effect on the contrast sensitivity. The larger the pixel size, the more photons ... 2. FACTOR: MATERIAL DENSITY- Density of material is a key factor in determining whether the contrast sensitivity will be great ... Lowering the energy will produce better contrast sensitivity. Figures 3 and 4 below are great examples of what can be detected ...
The King-Devick Color Contrast Sensitivity Chart in AMD View as PDF Take-Home Message The visual acuity of 85 patients with age ... Use of the King-Devick Variable Color Contrast Sensitivity Chart to differentiate stages of age-related macular degeneration ... Objective This study aimed to determine which colour contrast sensitivity differences exist in early to advanced age-related ...
We provide eyeglass consultations for low contrast sensitivity. Schedule an evaluation in Arlington or Mansfield, Texas. ... What is Low Contrast Sensitivity?. Poor contrast sensitivity is easiest to notice while driving at night or in foggy conditions ... Treatments for Contrast Sensitivity Issues in Arlington and Mansfield. This condition can be dangerous. If you have a hard time ... What Causes Low Contrast Sensitivity?. Several conditions can result in this issue. Common causes include:. *Diabetic ...
Contrast sensitivity. This man is a highly intelligent and astute observer He is an engineer with a PhD. He told me that he ... Contrast sensitivity manifests in glaucoma patient with no cataracts. June 12, 2020. Benjamin P. Casella, OD, FAAO ... Contrast sensitivity evaluates how well a person can distinguish an object from its background and it is an often overlooked ... He was kind enough to leave this with me so I could test contrast sensitivity on glaucoma patients. I thanked him and told him ...
Contrast sensitivity is the ability to discern an item from a very similar background. Its measured by the Pelli-Robson test, ... reduced contrast sensitivity means having poor vision acuity.. Why Contrast Sensitivity Matters. Contrast sensitivity is an ... What Is Contrast Sensitivity?. Contrast sensitivity, or CS, is the ability of your eyes to distinguish between the foreground ... Pelli-Robson Test and Contrast Sensitivity Home / Vision Education / Contrast Sensitivity Testing / Pelli-Robson Test ...
Factors Affecting Contrast Sensitivity in Intermittent Exotropia 의 이용 수, 등재여부, 발행기관, 저자, 초록, 목차, 참고문헌 등 논문에 관한 다양한 정보 및 관련논문 ... 대한안과학회 The Korean Journal of Ophthalmology Vol.34 No.5 Factors Affecting Contrast Sensitivity in Intermittent Exotropia ... Purpose: To determine whether contrast sensitivity (CS) can represent photophobia in intermittent exotropia (IXT) by ...
Quickly assess patient contrast sensitivity thresholds with the Pelli-Robson Contrast Sensitivity Chart. Includes 2 charts w/ ... Pelli Robson Contrast Sensitivity Chart Developed by Dr D Pelli of Syracuse University, New York and Dr J Robson of University ... utilises letters of the same size but with reducing contrast to provide a quick means of assessing patient contrast sensitivity ...
  • Determine the CS thresholds in terms of a contrast percentage under the following conditions. (
  • We found that contrast thresholds were lower than in a control condition without inducers, and that the threshold reduction was independent of the contrast polarity of the inducers. (
  • Glaucoma raises contrast detection thresholds, but our natural visual environment is dominated by high contrast that may remain suprathreshold in early to moderate glaucoma. (
  • Contrast detection thresholds for Gabor stimuli (SD, 0.75°) of four spatial frequencies (0.5, 1.0, 2.0, and 4.0 c/deg) were first measured at 10° eccentricity, both within and outside of visual field defects for participants with glaucoma. (
  • The Pelli-Robson chart utilises letters of the same size but with reducing contrast to provide a quick means of assessing patient contrast sensitivity thresholds. (
  • Overall, contrast thresholds for the migraine group were lower than those in the control group. (
  • In most cases, people with cataracts notice a significant improvement in both visual acuity and contrast sensitivity after cataract surgery. (
  • The patient can be easily screened in the examination chair for ETDRS acuity and contrast sensitivity. (
  • After the primary evaluation, iPad-based stereo acuity and contrast sensitivity tests were conducted using the subject's existing refractive correction. (
  • The visual acuity and contrast sensitivity were measured before and after PTK. (
  • Optical quality is a subjective construct that can only be described indirectly by objective metrics such as wavefront error measurements and visual quality metrics or functional data like visual acuity and contrast sensitivity. (
  • A person with normal visual acuity but poor contrast sensitivity might see the trees in the foreground clearly (high contrast), but have trouble seeing the contours of the mountains against the sky in the background (low contrast). (
  • Poor contrast sensitivity also can increase your risk of a fall if you fail to see that you need to step down from a curb onto similarly coloured pavement. (
  • Navigating spaces with stairs or curbs is similarly risky when you have poor contrast sensitivity. (
  • Poor contrast sensitivity is easiest to notice while driving at night or in foggy conditions where light may reflect and create a glare. (
  • Specifically, 96% had visual acuity levels less than age-expected values, 37% had poor contrast sensitivity and 31% failed the depth perception test. (
  • Low contrast sensitivity can be a symptom of certain eye conditions or diseases such as cataracts , glaucoma or diabetic retinopathy . (
  • Contrast sensitivity evaluates how well a person can distinguish an object from its background and it is an often overlooked symptom of glaucoma. (
  • The CSV-1000E provides a full contrast sensitivity curve, which is very useful for the evaluation of ocular disease (particularly cataracts, glaucoma, optic neuritis, diabetes and macular degeneration), contact lenses and refractive surgery. (
  • This study investigates the effect of glaucoma on the apparent contrast of visible stimuli. (
  • Despite decreased contrast sensitivity, people with glaucoma perceive the contrast of visible suprathreshold stimuli similarly to healthy controls. (
  • Bham HA, Dewsbery SD and Denniss J (2020) Unaltered perception of suprathreshold contrast in early glaucoma despite sensitivity loss. (
  • Although structural integrity and functional performance remained relatively unchanged, the improvement in glare affected mesopic [contrast sensitivity] is noteworthy, particularly in the context of the glare-related symptoms known to affect people with glaucoma. (
  • Reduced visual contrast sensitivity is often a symptom of a more serious eye condition, such as cataracts, glaucoma, or macular degeneration. (
  • Afterwards, the best corrected ocular diseases, including optic neuritis and visual acuity was determined on a subjec- glaucoma, where contrast sensitivity can be tive basis. (
  • Contrast sensitivity is one of the components of visual function, which is affected even in early subclinical stages of various eye diseases, including diabetic retinopathy. (
  • We present theoretical and practical aspects related to the evolution of contrast sensitivity before and after laser photocoagulation in diabetic retinopathy. (
  • There is still controversy about the effec- correction of the refractive error, the con- tiveness of contrast sensitivity as a screen- trast sensitivity was evaluated with a Cam- ing tool for diabetic retinopathy [12-17]. (
  • People with reduced visual contrast sensitivity may be able to read normally if the letters are dark and the background is light, or vice-versa. (
  • As with reading, poor visual contrast sensitivity doesn't affect the ability to see objects, except when these objects are the same or similar colors as their surroundings. (
  • Q: What Causes Reduced Visual Contrast Sensitivity? (
  • Difficulties with visual contrast sensitivity tend to be a symptom of another ocular problem. (
  • Q: How Can Visual Contrast Sensitivity Be Improved? (
  • If symptoms are present, your IALVS low vision eye doctor will provide you with treatment options, such as visual aids and devices to help you improve contrast sensitivity. (
  • [ 1 ] although permanent residual deficits in color vision and contrast and brightness sensitivity are common. (
  • Binocular contrast sensitivity function was measured with the Optec 6500 FACT contrast sensitivity chart at distance and at three lighting conditions (85 cd/m2 and 3 cd/m2 with and without glare) in 36 eyes of 18 patients implanted with the AcrySof ReSTOR aspheric SN6AD3 IOL and 40 eyes of 20 patients implanted with the Acri.LISA 366D IOL. (
  • The Pelli Robson contrast sensitivity chart tests your ability to detect letters that are gradually less contrasted with the white background as your eyes move down the chart. (
  • Probably the most widely used device to test contrast sensitivity is the Pelli Robson contrast sensitivity chart. (
  • Like a standard Snellen visual acuity chart, the Pelli Robson chart consists of horizontal lines of capital letters but instead of the letters getting smaller on each successive line, it is the contrast of the letters (relative to the chart background) that decreases with each line. (
  • Prior to assessing contrast sensitivity (CS) determine distance vision/visual acuity using the Snellen chart. (
  • None of the studies using the standard high contrast E Chart detected any vision loss. (
  • The CSV-1000E contrast sensitivity chart test face is the most widely used contrast sensitivity test in the world. (
  • The CSV-1000E Contrast Sensitivity Chart 1 provides randomized locations for the grating targets. (
  • The chart luminance was regularly checked acuity and Cambridge low-contrast grating using a spot photometer. (
  • Abnormal contrast sensitivity and color vision are present in almost all adults with ON even in the absence of a measurable decrease in visual acuity. (
  • Abnormal contrast sensitivity was ob- retinopathy, mild, moderate, severe, or very served in 27.1% of eyes with diabetic retin- severe non-proliferative diabetic retinopa- opathy, compared with 9.0% in unaffected thy (NPDR), early proliferative diabetic eyes. (
  • Spatio-temporal and temporal contrast sensitivity curves calculated with the model are compared with measurements published in literature. (
  • Comparison between the role of spatial and temporal contrast sensitivities in the association with reading may provide insight into how visual tasks (such as reading) are related to primary optical or neural (or both) effects. (
  • The contrast sensitivity was measured in mesopic and photopic background luminances, with glare (G) levels of 0-2 (G0, G1, and G2, respectively) and spatial frequencies at 1.5, 3, 6, 12, and 18 cycles per degree (cpd). (
  • ISRCTN13894787 ) were assessed using a range of psychophysical measures of visual function, including best corrected visual acuity (BCVA), letter contrast sensitivity (CS), mesopic and photopic CS, mesopic and photopic glare disability (GD), photostress recovery time (PRT), reading performance and subjective visual function, using the National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25). (
  • These bars can vary in width (spatial frequency) as well as contrast from target to target, to give a more thorough evaluation of how sensitive your eyes are to differences in contrast. (
  • Contrast sensitivity is a measurement of your ability to discern subtle differences between two objects. (
  • Objective This study aimed to determine which colour contrast sensitivity differences exist in early to advanced age-related macular degeneration (AMD) and examine the potential utility of the King-Devick Variable. (
  • When the first postoperative examination was not considered, there were no statistically significant differences in contrast sensitivity values at different postoperative periods . (
  • The AcrySof ReSTOR SN6AD3 and Acri.LISA aspheric IOLs provided contrast sensitivity within normal range under photopic conditions and a reduction in contrast sensitivity under mesopic conditions, with no significant differences between the two brands. (
  • Purpose: To determine if incidence of contrast sensitivity (CS) impairment differs by generation and identify factors to explain these differences. (
  • The contrast is represented by a numeric value named average gradient, and can be determined by density differences in two areas of a radiograph. (
  • However, sensitivity to achromatic contrasts - the ability to discern luminance difference between two objects or an object and its background - has been shown to be lower in birds compared with other vertebrates. (
  • We conducted a comparative study to evaluate the achromatic contrast sensitivity of 32 bird species from 12 orders using the optocollic reflex technique. (
  • We found a low achromatic contrast sensitivity for all avian species studied compared with other vertebrates (except small mammals), with high variability between species. (
  • A statistically significant increase in mesopic contrast sensitivity under glare conditions was noted at 18 months in the treatment group, but not in the placebo group. (
  • The grating contrast or spatial frequency for which 50% of infants gave a statistically significant VEP was taken as a measure of threshold. (
  • Guessing ensures the use of the three-alternative, forced-choice test method, known to improve the accuracy of contrast threshold measurement. (
  • Each correct letter has a contrast threshold value of 0.05 log units however scoring in terms of log units is reserved for research. (
  • The results suggest that the reduction of contrast threshold in contour gaps is independent of the brightness perceived in these gaps and of the formation of an illusory figure. (
  • Processes that cause contrast threshold reduction in contour gaps also seem to operate independently of figural completion. (
  • Contrast sensitivity defines the threshold between the visible and invisible, which has obvious significance for basic and clinical vision science. (
  • Fechner's 1860 review reported that threshold contrast is 1% for a remarkably wide range of targets and conditions. (
  • Subsequently, the contrast of a central Gabor was matched to that of a peripheral Gabor with contrast fixed at two times or four times the detection threshold. (
  • The contrast sensitivity is measured in log MAR units, and the score expresses the reciprocal of the threshold contrast using the Weber contrast ratio. (
  • For reference stimuli at four times the detection contrast, matched contrast ratios were similar across all three groups (P = 0.58). (
  • These results are consistent with the findings reported by Shepherd (2011), in showing enhanced contrast sensitivity in migraine with aura for small, rapidly presented targets, and no difference in the lateral interactions between target and mask stimuli compared with a control group. (
  • Targeted disruption of the gene encoding D4Rs reduces the amplitude of the contrast sensitivity rhythm by reducing daytime sensitivity and abolishes the rhythmic expression of Npas2 and Adcy1 mRNA in the ganglion cell layer (GCL) of the retina. (
  • These high light levels tend to saturate the retina and therefore decrease finer levels of contrast sensitivity. (
  • The major function of dark (gray, green, or brown) sunglasses is to allow the retina to remain at its normal level of contrast sensitivity. (
  • After surgery, contrast sensitivity and wavefront measurements as well as tilt and decentration measurements were performed. (
  • Measurements on the negative portion of the x-axis are beyond the visual range when specimens were diluted 1:250, yet still detectable by thermal contrast. (
  • The contrast sensitivity function (CSF) is routinely assessed in clinical evaluation of vision and is the primary limiting factor in how well one sees. (
  • Contrast sensitivity is a very important measure of visual function, especially in situations of low light, fog or glare, when the contrast between objects and their background is often reduced. (
  • The tester records the results to produce a contrast sensitivity function (CSF) or curve. (
  • The aim of this study was to characterize the contrast sensitivity function (CSF) of adolescents and young adults. (
  • The spectral response of S-cones peak at 420 nm, M-cones at 534 nm, and L-cones at 564 nm, with significant overlap in their spectral response ranges and varying degrees of sensitivity at these range of wavelengths specified by the function m k (λ), k = r, g, b, as depicted in Figure 2.1(a) . (
  • where m k (λ) is the wavelength sensitivity function (also known as the color matching function) of the k th cone type or color sensor. (
  • Contrast sensitivity, the ability to distinguish the relative difference in luminance of an object from its surrounding or adjacent objects, is a useful measure of visual function. (
  • We compared the contrast sensitivity of GCD2 patients before and after phototherapeutic keratectomy (PTK) to evaluate the perioperative visual function in these patients. (
  • There are numerous variants of the LEA test which can be used to assess the visual capabilities of near vision and distance vision, as well as several other aspects of occupational health, such as contrast sensitivity, visual field, color vision, visual adaptation, motion perception, and ocular function and accommodation (eye). (
  • Visual acuity charts only measure the eases, history of previous ocular surgery high frequency component of the contrast or photocoagulation and systemic diseases sensitivity function and are markedly af- other than diabetes. (
  • Therefore, the diabetes, mode of control and last blood contrast sensitivity function curve gives glucose level, checked in the past month. (
  • Sensitivity analyses were performed using different kidney function surveillance definitions. (
  • Treating clinic remained a significant predictor of kidney function surveillance in all sensitivity analyses. (
  • Results were similar in sensitivity analyses excluding those with cataract, age-related macular degeneration, or visual acuity impairment. (
  • Both IOLs provided contrast sensitivity within the normal range in photopic conditions. (
  • If the eye doctor identifies a problem with contrast sensitivity, the main form of treatment is to treat the underlying condition, which usually improves contrast responsiveness as well. (
  • Conclusions: In FED, DMEK may not only be effective for obtaining a higher visual acuity but particularly improving the contrast sensitivity may also lead to better subjective optical performance. (
  • Each row or circular grouping of patches tests at a specific spatial frequency (cycles per degree), which measures the observer's sensitivity to a particular object size. (
  • Spatial frequency had a minimal effect on matched contrast ratios. (
  • If your optometrist determines that you need a contrast sensitivity test, it likely will be administered after a standard visual acuity test and before your pupils are dilated . (
  • At the recent ARVO meeting in Seattle, a number of vision scientists described studies in which significant vision loss could not be detected by standard visual acuity, but could be detected by contrast sensitivity and glare testing. (
  • The Pelli Robson test was designed specifically to determine if a patient has difficulties with contrast sensitivity. (
  • Pelli-Robson contrast sensitivity and Farnsworth-Munsell 100 hue color vision tests were performed. (
  • We then performed an analysis to test for potential variability in contrast sensitivity depending on the corneal diameter to the axial length ratio, a proxy of the retinal image brightness. (
  • It shares with optical imaging, that it uses non-ionizing radiation and provides higher contrast and higher sensitivity than ultrasound imaging. (
  • This reduction cannot be explained by a simple summation of stimulus contrast and induced brightness. (
  • Figures 3 and 4 below are great examples of what can be detected when utilizing tube to detector distance reduction to increase contrast. (
  • Under low lighting conditions, a reduction in contrast sensitivity for both lenses, particularly at higher spatial frequencies, was noted. (
  • The CSV-1000-1.5CPD is a special test face designed specifically for Food and Drug Administration clinical trials which require the testing of contrast sensitivity at 1.5 cycles/degree under mesopic lighting conditions. (
  • We examined the contributions of brightness enhancement, illusory figure formation and figural completion to changes in contrast sensitivity in contour gaps. (
  • However, if the letters and the background are of a similar color or level of brightness or faintness, people with reduced visual sensitivity may struggle to read the text. (
  • To evaluate contrast sensitivity after posterior chamber phakic intraocular lens (PIOL) implantation for the correction of high myopia . (
  • Purpose: The aim of this study is to evaluate contrast sensitivity, color vision, and subjective patient satisfaction after Descemet membrane endothelial keratoplasty (DMEK) in patients with bilateral Fuchs endothelial dystrophy (FED). (
  • Sensitivity to tumor microvasculature without contrast agents in high spectral and spatial resolution MR images. (
  • This research investigated whether high spectral and spatial resolution (HiSS) MRI detects tumor vasculature without contrast agents, based on the sensitivity of the water resonance line shape to tumor blood vessels. (
  • A more user friendly approach is to score in terms of contrast percentage. (
  • A number of studies have shown that aspherical IOLs perform better compared to conventional spherical ones in terms of contrast sensitivity (CS), particularly under mesopic conditions [ 2 , 3 ]. (
  • The VCTS uses highly controlled advanced photographic and printing techniques to present a series of sine-wave gratings at carefully calibrated levels of contrast. (
  • The scientists found that contrast sensitivity was enhanced when the amount of stimulation of melanopsin cells increased by using light in a special spectrum. (
  • Changes in contrast sensitivity also can occur after LASIK , PRK and other types of refractive surgery. (
  • Some people who have refractive surgery like LASIK may also experience this problem, although some actually report improved sensitivity. (
  • In GCD2 patients, the contrast sensitivity increased significantly after PTK. (
  • Contrast sensitivity of blast-exposed animals decreased significantly by 20% 1 day after blast and did not recover by 8 weeks. (
  • proposed three decades ago that human frequency sensitivity may derive from the augmentation necessary for more effective retinal picture interpretation. (
  • For a study, researchers reconsidered the role of low-level vision tasks in explaining contrast sensitivity functions (CSFs) in light of the current trend of employing artificial neural networks for vision research and the current understanding of retinal image representations. (
  • As an illustration, the best CNN (in the collection of basic architectures examined for retinal signal augmentation) reproduced the CSFs with a root mean square error of 11% of the maximal sensitivity. (
  • Our study demonstrates a circadian rhythm of contrast sensitivity that peaks during the daytime, and that its regulation involves interactions of D4Rs, the clock gene Npas2 , and the clock-controlled gene adenylyl cyclase 1 ( Adcy1 ) in a subset of retinal ganglion cells (RGCs). (
  • However, the underlying cellular and molecular mechanisms through which retinal dopamine modulates contrast sensitivity have not been elucidated. (
  • The size of the sine-wave gratings, the contrast levels, and their tilt are all based on current vision science and empirical data. (
  • Please review the images and text below to learn about the various contrast sensitivity test faces that can be used with the CSV-1000. (
  • The blinking square contrast sensitivity test involves showing the patient target squares at various contrast levels in different quadrants of the screen. (
  • Our results indicate that the contrast sensitivity rhythm is modulated by D4Rs via a signaling pathway that involves NPAS2-mediated circadian regulation of Adcy1 . (
  • These results suggest that the process of development and maturation of the visual perception of contrast interacts differently with the mechanisms that process spatial frequencies. (
  • This results in better contrast resolution while giving up some pixel resolution. (
  • These results suggest possible compensation for sensitivity loss in the visual system. (
  • These results suggest that tumor microvasculature can be detected using HiSS imaging without the use of contrast agents. (
  • Conversely, some people achieve better contrast sensitivity and night vision after LASIK, compared with their vision with glasses or contact lenses before the procedure. (
  • A new study published in Vision Research has highlighted that contrast sensitivity can be enhanced by light in a specific spectrum. (
  • A healthy contrast sensitivity level lets you enjoy better vision in various aspects, such as having a normal visual field. (
  • Generally, reduced contrast sensitivity means having poor vision acuity. (
  • The patients were asked to participate in a series of tests to assess their vision, including a visual acuity test, a contrast sensitivity test and a depth perception test. (
  • The visual acuity test measured the patients' overall vision functioning, while the contrast sensitivity and depth perception tests focused on the patients' ability to distinguish between objects of different shades of color and the ability to determine relative distances between and within objects. (
  • For evaluation of eye disease , contrast sensitivity usually is tested on each eye individually. (
  • Hence, quantifying contrast sensitivity before surgery may aid in the decision for surgery, and in the evaluation of surgical outcome. (
  • People who have a hard time distinguishing contrasts can find it difficult to see in the daytime as well. (
  • What is a contrast sensitivity test? (
  • A contrast sensitivity test measures your ability to distinguish between finer and finer increments of light versus dark (contrast). (
  • Contrast sensitivity testing often isn't included in a routine eye test. (
  • Your optometrist might perform the test because of a specific visual complaint you have or because he or she suspects you have a condition that is affecting your ability to discern contrast. (
  • Other, more sophisticated devices also may be used to test your contrast sensitivity. (
  • The low frequencies test sensitivity to very large objects, while on the other end, high frequencies measure sensitivity to very small objects. (
  • Each test frequency begins with a high level of contrast, which diminishes progressively with each succeeding patch. (
  • Can Your Eyes Pass The Contrast Sensitivity Test? (
  • The following test is based on tests issued by eye doctors in order to test a patient's ability to recognize changes in contrast. (
  • The test was named after them, and it's now considered the gold standard in contrast sensitivity measurement. (
  • The test could be helpful for almost anyone, but some conditions can impact your ability to discern contrast. (
  • Purpose: To determine whether contrast sensitivity (CS) can represent photophobia in intermittent exotropia (IXT) by comparingthe CS test with and without glare stimulus, and to analyze the factors of IXT affecting CS. (
  • However, in this test, instead of shrinking in size with each descending row, the letters show less contrast, appearing in ever weaker shades of gray against a white background. (
  • The test is divided into six squares, starting with a high-contrast square, and with each subsequent square, the contrast is reduced in increments of 0.3 log MAR units. (
  • A) Prediction of cryptococcal antigen titer based on laser thermal contrast measurement and concept of lateral flow immunochromatographic assay (LFA) thermal contrast measurement in which a laser irradiates the test line in the LFA ( 19 ). (
  • L'analyse bactériologique du liquide céphalorachidien (LCR) et un test de sensibilité aux antibiotiques de la bactérie mise en culture étaient disponibles dans un tiers des hôpitaux. (
  • B) Association of measured semiquantitative LFA cryptococcal antigen (CRAG) titer starting at a 1:250 dilution by the predicted CRAG titer based on thermal contrast measurement. (
  • Contrast sensitivity , or CS, is the ability of your eyes to distinguish between the foreground and the background. (
  • Thus a Loss of low-frequency contrast sensitivity total number of 154 eyes of 80 patients were has been reported to reduce the ability to evaluated. (
  • People with contrast sensitivity difficulties may start realizing they have a problem if they keep tripping over curbs or steps because they don't see them clearly. (
  • Se realizó una búsqueda en bases de datos HINARI, PubMed y Scopus en idioma español e inglés, se incluyeron artículos originales y de revisión con un máximo de cinco años desde su publicación. (
  • As the vegetation develops from spring to autumn, the sensitivity to meteorological drought increases, across all 7 investigated biomes, although the strength and time scale differs across regions. (
  • The stronger association between temporal CS and reading speed is suggested to reflect a high sensitivity for neural integrity of temporal CS. (
  • Contrast sensitivity after posterior chamber phakic intraocular lens implantation for high myopia. (
  • In separate blocks of trials, the target was presented alone, or flanked by two additional collinear, high contrast Gabors. (
  • We tested whether regions with high contrast in FC images (FCIs) contain vasculature by comparing FCIs with CE-MRI as the "gold standard" of vascular density. (
  • Improved lighting in dialysis units, large magnifiers, and modified educational materials with large type and high contrasts can be inexpensive and effective ways to improve patient functioning. (
  • We found that the very act of action video game playing also enhanced contrast sensitivity, providing a complementary route to eyesight improvement. (
  • However, the molecular probes used for most of these studies were contrast agents simply adopted from other optical imaging modalities. (
  • This research allows to create optimized molecular specific contrast enhanced photothermal stable probes which can aid photoacoustic imaging and image guided photothermal cancer therapy. (
  • 2. FACTOR: MATERIAL DENSITY- Density of material is a key factor in determining whether the contrast sensitivity will be great, average, or poor. (
  • Less dense materials show better contrast sensitivity than higher density materials. (
  • Later, the density of those X-rays was measured and the characteristic curves were built in order to determine their sensitometric properties, such as contrast, indicative value of sensibility, and latitude. (
  • However, the applicability, importance level, and achievement condition of a radiograph depend on the quality of the image obtained, being a good quality radiograph the one presenting maximum detail, minimum distortion, and medium levels of density and contrast 2 . (