Contrast Sensitivity: 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.Visual Acuity: 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.Vision Tests: A series of tests used to assess various functions of the eyes.Glare: 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)Sensory Thresholds: The minimum amount of stimulus energy necessary to elicit a sensory response.Amblyopia: 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.Vision Disorders: 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).Psychophysics: 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.Night Vision: 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.Sensitivity and Specificity: 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)Vision, Ocular: The process in which light signals are transformed by the PHOTORECEPTOR CELLS into electrical signals which can then be transmitted to the brain.Color Perception: 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.Photic Stimulation: Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity.Color Vision Defects: 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.Visual Fields: The total area or space visible in a person's peripheral vision with the eye looking straightforward.Pattern Recognition, Visual: Mental process to visually perceive a critical number of facts (the pattern), such as characters, shapes, displays, or designs.Space Perception: The awareness of the spatial properties of objects; includes physical space.Flicker Fusion: The point or frequency at which all flicker of an intermittent light stimulus disappears.Visual Pathways: 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.Evoked Potentials, Visual: The electric response evoked in the cerebral cortex by visual stimulation or stimulation of the visual pathways.Form Perception: The sensory discrimination of a pattern shape or outline.Fovea Centralis: 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)Orthoptics: 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.Adaptation, Ocular: 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)Pupil: The aperture in the iris through which light passes.Vision, Binocular: The blending of separate images seen by each eye into one composite image.Color Perception Tests: Type of vision test used to determine COLOR VISION DEFECTS.Myopia: 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.Color Vision: 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).Strabismus: 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)Lenses, Intraocular: Artificial implanted lenses.Cataract: 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, Low: 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.).Discrimination (Psychology): Differential response to different stimuli.Geniculate Bodies: 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.Visual Field Tests: Method of measuring and mapping the scope of vision, from central to peripheral of each eye.Optics and Photonics: 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.Visual Perception: The selecting and organizing of visual stimuli based on the individual's past experience.Nystagmus, Optokinetic: Normal nystagmus produced by looking at objects moving across the field of vision.Eyeglasses: 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.Retina: 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.Keratomileusis, Laser In Situ: 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.Perceptual Disorders: 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.Scotoma: 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.Dark Adaptation: Adjustment of the eyes under conditions of low light. The sensitivity of the eye to light is increased during dark adaptation.Optic Neuritis: 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).Orientation: Awareness of oneself in relation to time, place and person.Lighting: 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, Ocular: Refraction of LIGHT effected by the media of the EYE.Macaca nemestrina: 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.Refractive Errors: Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus.Vision, Monocular: Images seen by one eye.Accommodation, Ocular: 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)Motion Perception: The real or apparent movement of objects through the visual field.Visual Cortex: Area of the OCCIPITAL LOBE concerned with the processing of visual information relayed via VISUAL PATHWAYS.Retinal Cone Photoreceptor Cells: 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.Ocular Physiological Phenomena: Processes and properties of the EYE as a whole or of any of its parts.Light: That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.Macular Degeneration: 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.Glaucoma: 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)Dyslexia: 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)Visually Impaired Persons: Persons with loss of vision such that there is an impact on activities of daily living.Depth Perception: Perception of three-dimensionality.Vision Screening: 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.Anisometropia: A condition of an inequality of refractive power of the two eyes.Fixation, Ocular: The positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye.Sensory Deprivation: The absence or restriction of the usual external sensory stimuli to which the individual responds.Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.Glaucoma, Open-Angle: Glaucoma in which the angle of the anterior chamber is open and the trabecular meshwork does not encroach on the base of the iris.Fluspirilene: A long-acting injectable antipsychotic agent used for chronic schizophrenia.Photometry: Measurement of the various properties of light.Astigmatism: 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)Mesopic Vision: 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.Contact Lenses: Lenses designed to be worn on the front surface of the eyeball. (UMDNS, 1999)Cats: 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)Orthokeratologic Procedures: 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.Afterimage: Continuation of visual impression after cessation of stimuli causing the original image.Psychophysiology: The study of the physiological basis of human and animal behavior.Optic Nerve Diseases: 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.Models, Psychological: Theoretical representations that simulate psychological processes and/or social processes. These include the use of mathematical equations, computers, and other electronic equipment.Aberrometry: 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.EthylaminesCataract Extraction: The removal of a cataractous CRYSTALLINE LENS from the eye.Size Perception: The sensory interpretation of the dimensions of objects.Retinal Ganglion Cells: 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: 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.Automobile Driving: 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.Color: The visually perceived property of objects created by absorption or reflection of specific wavelengths of light.Subretinal Fluid: An exudate between the RETINA and CHOROID from various sources including the vitreous cavity, SUBARACHNOID SPACE, or abnormal vessels.Nature: 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)Presbyopia: The normal decreasing elasticity of the crystalline lens that leads to loss of accommodation.Reproducibility of Results: 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.Refractive Surgical Procedures: 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.Electroretinography: Recording of electric potentials in the retina after stimulation by light.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Retinal DiseasesDiabetic Retinopathy: 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.Perceptual Masking: The interference of one perceptual stimulus with another causing a decrease or lessening in perceptual effectiveness.ReadingHalogens: A family of nonmetallic, generally electronegative, elements that form group 17 (formerly group VIIa) of the periodic table.Aphakia, Postcataract: Absence of the crystalline lens resulting from cataract extraction.Attention: Focusing on certain aspects of current experience to the exclusion of others. It is the act of heeding or taking notice or concentrating.Fundus Oculi: 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)Ophthalmoscopes: Devices for examining the interior of the eye, permitting the clear visualization of the structures of the eye at any depth. (UMDNS, 1999)Injections, Intraocular: The administration of substances into the eye with a hypodermic syringe.Lens Implantation, Intraocular: 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.Perceptual Distortion: Lack of correspondence between the way a stimulus is commonly perceived and the way an individual perceives it under given conditions.Photorefractive Keratectomy: 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.Differential Threshold: The smallest difference which can be discriminated between two stimuli or one which is barely above the threshold.Distance Perception: 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.Prospective Studies: 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.Eye Diseases: Diseases affecting the eye.Reaction Time: The time from the onset of a stimulus until a response is observed.Melopsittacus: A genus, commonly called budgerigars, in the family PSITTACIDAE. In the United States they are considered one of the five species of PARAKEETS.Pseudophakia: Presence of an intraocular lens after cataract extraction.Fluorescein Angiography: 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.Miotics: 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.Keratotomy, Radial: A procedure to surgically correct REFRACTIVE ERRORS by cutting radial slits into the CORNEA to change its refractive properties.Duane Retraction Syndrome: 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.Retinitis Pigmentosa: Hereditary, progressive degeneration of the neuroepithelium of the retina characterized by night blindness and progressive contraction of the visual field.Models, Neurological: 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.Lasers: 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.Psychometrics: Assessment of psychological variables by the application of mathematical procedures.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Eye: 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.Esotropia: 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.Ocular Hypertension: A condition in which the intraocular pressure is elevated above normal and which may lead to glaucoma.Cues: Signals for an action; that specific portion of a perceptual field or pattern of stimuli to which a subject has learned to respond.Tomography, Optical Coherence: 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.Practice (Psychology): 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.Keratoconus: 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)Vigabatrin: 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)Macula Lutea: 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)Intraocular Pressure: The pressure of the fluids in the eye.Dominance, Ocular: 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.Hyperopia: 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)AlabamaNeurons: 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.Eye Movements: Voluntary or reflex-controlled movements of the eye.Age Factors: 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.Macular Edema: 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)Optic Nerve: 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.Child Development: The continuous sequential physiological and psychological maturing of an individual from birth up to but not including ADOLESCENCE.Lens, Crystalline: 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.Cornea: 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)Photoreceptor Cells: 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.Retinal Vessels: The blood vessels which supply and drain the RETINA.Diagnostic Techniques, Ophthalmological: Methods and procedures for the diagnosis of diseases of the eye or of vision disorders.Macaca: 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.Rotation: 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)Signal Detection, Psychological: 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.)Macaca mulatta: 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.Case-Control Studies: 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.Laser Coagulation: The use of green light-producing LASERS to stop bleeding. The green light is selectively absorbed by HEMOGLOBIN, thus triggering BLOOD COAGULATION.Choroidal Neovascularization: A pathological process consisting of the formation of new blood vessels in the CHOROID.Scattering, Radiation: 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)Psychomotor Performance: The coordination of a sensory or ideational (cognitive) process and a motor activity.Diagnosis, Computer-Assisted: Application of computer programs designed to assist the physician in solving a diagnostic problem.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Follow-Up Studies: 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.Postoperative Period: The period following a surgical operation.

*  WaveLight® Refractive Flap Accuracy Study - Full Text View - ClinicalTrials.gov

Contrast sensitivity was assessed at spatial frequencies of 3, 6, 12, and 18 cycles per degree (cpd), where 3.0 cpd = A, 6.0 ... Contrast sensitivity (ie, the ability to detect slight changes in luminance before they become indistinguishable) was assessed ... Mean Contrast Sensitivity (CS) [ Time Frame: Baseline/Screening (Day 0), Month 1 Postoperative, Month 3 Postoperative, Month 6 ... A higher numeric value represents better contrast sensitivity. Both eyes contributed to the analysis. ...

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We simultaneously measured contrast sensitivity and neural contrast response functions and compared measurements in common ... Contrast sensitivity, V1 neural activity, and natural vision Message Subject (Your Name) has sent you a message from Journal of ... We found that contrast sensitivity and V1 activity are correlated and that the relationship is similar in laboratory and ... Contrast sensitivity, V1 neural activity, and natural vision. James E. Niemeyer, Michael A. Paradiso ...

*  Age-related changes in contrast gain related to the M and P pathways | JOV | ARVO Journals

Contrast sensitivity and light adaptation in photoreceptors or in the retinal network. Contrast sensitivity. (pp. 103-116). ... This pattern of contrast sensitivity loss is consistent with a reduction in the contrast gain slope of the underlying mechanism ... Specifically, measures of contrast sensitivity for (L-M) varying patterns reveal an average 0.25 log unit loss in sensitivity ... Because contrast sensitivity is thought to be proportional to the contrast gain of the underlying mechanism (Kaplan & Shapley, ...

*  Aerial perspective - Wikipedia

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 his or her contrast sensitivity.[1] ...

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Depressed contrast sensitivity was not well correlated with abnormal adaptation to contrast. In patients whose contrast ... between abnormal contrast sensitivity and abnormal contrast adaptation is that some patients with normal contrast sensitivity ... sensitivity losses were restricted to a band of spatial frequencies, we found no evidence that abnormalities of contrast ... we accounted for this in our patient group by showing that multiple sclerosis had caused a depression of contrast sensitivity ...

*  Contrast Sensitivity - Technology - LASIK - Flaum Eye Institute - University of Rochester Medical Center

Contrast Sensitivity During the pre-operative evaluation we'll test your contrast. sensitivity with a special eye chart that ... The use of contrast sensitivity testing by the Flaum Eye Institute Refractive Surgery Center team allows us to detect subtle ... It is well known that refractive surgery causes a temporary mild decrease in contrast sensitivity immediately after surgery. ... Certain factors can result in more persistent losses in contrast sensitivity. These include treatment using older broad beam ...

*  British Library EThOS: Contrast sensitivity as an indicator of binocular function

Binocular contrast function Human physiology Medicine Optics ... Contrast sensitivity as an indicator of binocular function ...

*  British Library EThOS: Spatial contrast sensitivity and external noise: applications to optical and neural modulation transfer...

... frequency on contrast sensitivity resulting in the extension of the new contrast detection model describing the human contrast ... Spatial contrast sensitivity and external noise: applications to optical and neural modulation transfer functions ... According to the model the human contrast detection system comprises low-pass filtering due to ocular optics, addition of light ...

*  Visual Outcomes And Contrast Sensitivity After Myopic Wavefront-Optimized Lasik With Nexisvision Shield Or Bandage Contact Lens...

Visual Outcomes And Contrast Sensitivity After Myopic Wavefront-Optimized Lasik With Nexisvision Shield Or Bandage Contact Lens ...

*  Visual Outcomes And Contrast Sensitivity After Myopic Wavefront-Optimized Lasik With Nexisvision Shield Or Bandage Contact Lens...

Contrast Sensitivity [ Time Frame: Immediate, 30 minutes, 1 hour, 2 hour, and 4 hours ]. Change in contrast sensitivity ... Visual Outcomes And Contrast Sensitivity After Myopic Wavefront-Optimized Lasik With Nexisvision Shield Or Bandage Contact Lens ... Historically, LASIK has been reported to decrease contrast sensitivity post operatively and patients have been advised to take ... Evaluate visual outcomes and contrast sensitivity for subjects undergoing bilateral myopic LASIK with a Nexisvision Shield or ...

*  Intraindividual comparison of color perception and contrast sensitivity with and without a blue light-filtering intraocular...

Regarding contrast sensitivity, 5 patients (21.7%) indicated noticeable difference between the two eyes. Contrast sensitivity ... Regarding contrast sensitivity, 5 patients (21.7%) indicated noticeable difference between the two eyes. Contrast sensitivity ... and contrast sensitivity with and without glare (Contrast Sensitivity Pattern Generator). Information about subjective ... and contrast sensitivity with and without glare (Contrast Sensitivity Pattern Generator). Information about subjective ...

*  Metrovision - Contrast sensitivity

The evaluation of the contrast sensitivity function presents much more sensitivity than the "standard" visual acuity ... The contrast sensitivity test is useful in several clinical applications:. • the pre and post op evaluation in cataract and ... The results of the exam are represented as a curve (here in red) giving the contrast sensitivity versus spatial frequency.. The ... Effect of contrast sensitivity and wavefront aberration improvements on the quality of daily vision. ...

*  Graphs | Additional Graphs | Contrast Sensitivity

You may display graphs of the mean photopic and mesopic contrast sensitivity in a logMar scale base on measurements with the ... Starting from Version 4.07 Datagraph med supports the HACSS contrast sensitivity test. Defaults can be set under 'Chart Options ... The dashed lines represent the normal range for photopic contrast sensitivity for a younger population between 20 and 50 years ... If set to HACSS contrast graphs will have 5 frequencies starting from 1.5 cpd. ...

*  Women In Astronomy: Why So Few? Contrast-Sensitivity Ability

... "contrast-sensitivity ability," women assessed their contrast-sensitivity ability lower than men did. When this ability was ... In the same fictitious skill of "contrast sensitivity," students were asked, "How high would you have to score to be convinced ... Correll describes this fictitious ability to detect correct proportions of black and white as "contrast-sensitivity ability." ...

*  Mars Perceptrix | accuracy and convenience in contrast sensitivity testing

Unlike other contrast tests that assess visual acuity using low contrast targets, the Mars tests are true contrast sensitivity ... Mars Contrast Sensitivity Tests The choice of eye care professionals, occupational testers, and clinical researchers around the ... arbitrarily chosen contrast. With the Mars tests, it is the contrast, and not the letter (or numeral) size, which diminishes ... Each chart is printed with 48 different contrast levels, declining gradually in 0.04 log unit steps - the finest steps ...

*  Influence of Microsaccades on Contrast Sensitivity: Theoretical Analysis and Experimental Results | JOV | ARVO Journals

Influence of Microsaccades on Contrast Sensitivity: Theoretical Analysis and Experimental Results Naghmeh Mostofi; Marco Boi; ... No benefit of microsaccades on contrast sensitivity was observed with a 10 cycles/deg grating. In both cases, however, all ... We then measured the influences of microsaccades on contrast sensitivity in a 2AFC experiment in which subjects reported the ... We show that, in agreement with theoretical predictions, contrast sensitivity slightly improved in the trials with one or more ...

*  OSA | Modulation transfer functions and contrast sensitivity through low vision telescopes

Modulation transfer functions and contrast sensitivity through low vision telescopes Milton Katz, Dean Yager, Alan Lewis, Karl ... to predict changes in contrast sensitivity functions (CSF) through them. We measured the CSFs of visually normal and aphakic ... "Modulation transfer functions and contrast sensitivity through low vision telescopes," Appl. Opt. 28, 1103-1109 (1989) ... Our results suggest that cascading (multiplying the contrast of the instrumental MTF with the unaided CSF at each spatial ...

*  Investigating the mechanisms that may underlie the reduction in contrast sensitivity during dynamic accommodation | JOV | ARVO...

Predicting individual contrast sensitivity functions from acuity and letter contrast sensitivity measurements ... if the reduction of contrast sensitivity was caused by this corollary discharge signal, reduced contrast sensitivity would have ... Relative sensitivity expressed as the ratio between contrast sensitivity measurements during dynamic and steady-state ... Relative sensitivity expressed as the ratio between contrast sensitivity measurements during dynamic and steady-state ...

*  Visual acuity and contrast sensitivity after posterior lamellar keratoplasty - Danish National Research Database-Den Danske...

Department of Clinical Medicine - The Department of Ophthalmology, Department of Clinical Medicine, Health, Aarhus ...

*  Dissociable prior influences of signal probability and relevance on visual contrast sensitivity - Nuffield Department of...

Dissociable prior influences of signal probability and relevance on visual contrast sensitivity ... Dissociable prior influences of signal probability and relevance on visual contrast sensitivity ...

*  Dissociable prior influences of signal probability and relevance on visual contrast sensitivity. - Oxford centre for Human...

This approach allowed us to estimate separately the sensitivity of true and false positives to parametric changes in signal ... Here, we reassessed the prior influences of signal probability and relevance on visual contrast detection using a reverse- ... We found that signal probability and relevance both increased energy sensitivity, but in dissociable ways. Cues predicting the ... However, conventional analyses that estimate sensitivity and bias by comparing true- and false-positive rates offer limited ...

*  Enhanced sensitivity and contrast with bimodal atomic force microscopy with small and ultra-small amplitudes in ambient...

Enhanced sensitivity and contrast with bimodal atomic force microscopy with small and ultra-small amplitudes in ambient ... CitacióSantos, S. Enhanced sensitivity and contrast with bimodal atomic force microscopy with small and ultra-small amplitudes ... enhanced contrast, and minimally invasive mapping. Fractions of meV of energy dissipation are shown to provide contrast above ... contact with the adsorbed water layers while the second mode amplitude and phase provide enhanced contrast and sensitivity. ...

*  Sensitivity enhancement of NIR fluorescence contrast agent utilizing gold nanoparticles. - PubMed - NCBI

Sensitivity enhancement of NIR fluorescence contrast agent utilizing gold nanoparticles.. Kang KA1, Wang J, O'Toole MG, Nantz M ...

*  Contrasting insulin sensitivity of endogenous glucose production rate in subjects with hepatocyte nuclear factor-1 beta and -1...

Contrasting insulin sensitivity of endogenous glucose production rate in subjects with hepatocyte nuclear factor-1 beta and -1 ... Contrasting insulin sensitivity of endogenous glucose production rate in subjects with hepatocyte nuclear factor-1 beta and -1 ...

*  OSA | Objects to Test the Sensitivity of Phase Contrast and Interference Microscopes*†

E. Menzel, "Objects to Test the Sensitivity of Phase Contrast and Interference Microscopes*†," J. Opt. Soc. Am. 47, 563-563 ( ... Objects to Test the Sensitivity of Phase Contrast and Interference Microscopes E. Menzel ... phase-contrast objective shows a path difference of 80 A with rather good contrast. ... To test the sensitivity of a microscope in distinguishing variations of optical thickness in an object, it is useful to have ...

LogMAR chart: A LogMAR chart comprises rows of letters and is used by ophthalmologists and vision scientists to estimate visual acuity. This chart was developed at the National Vision Research Institute of Australia in 1976, and is designed to enable a more accurate estimate of acuity as compared to other charts (e.Landolt CGlare (vision): Glare is difficulty seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions.Percolation threshold: Percolation threshold is a mathematical concept related to percolation theory, which is the formation of long-range connectivity in random systems. Below the threshold a giant connected component does not exist; while above it, there exists a giant component of the order of system size.AmblyopiaOperation Eyesight Universal: Operation Eyesight Universal is a Canada-based international development organisation, founded in 1963. It works to prevent avoidable blindness and to cure blindness that is treatable.Korte's law: In psychophysics, Korte's law, also known more completely as Korte's third law of apparent motion, is an observation relating the phenomenon of apparent motion to the distance and duration between two successively presented stimuli. It was originally proposed in 1915 by Adolf Korte.Tactical light: A tactical light is a flashlight used in conjunction with a firearm to aid low light target identification, allowing the marksman to simultaneously aim and illuminate the target. Tactical lights can be handheld or mounted to the weapon with the light beam parallel to the bore.Assay sensitivity: Assay sensitivity is a property of a clinical trial defined as the ability of a trial to distinguish an effective treatment from a less effective or ineffective intervention. Without assay sensitivity, a trial is not internally valid and is not capable of comparing the efficacy of two interventions.Gene therapy for color blindness: Gene therapy for color blindness is an experimental gene therapy aiming to convert congenitally colorblind individuals to trichromats by introducing a photopigment gene that they lack. Though partial color blindness is considered only a mild disability and is controversial whether it is even a disorder, it is a condition that affects many people, particularly males.Meridian (perimetry, visual field): Meridian (plural: "meridians") is used in perimetry and in specifying visual fields. According to IPS Perimetry Standards 1978 (2002): "Perimetry is the measurement of [an observer's] visual functions ...Flicker (screen): Flicker is a visible fading between cycles displayed on video displays, especially the refresh interval on cathode ray tube (CRT) based computer screens. Flicker occurs on CRTs when they are driven at a low refresh rate, allowing the brightness to drop for time intervals sufficiently long to be noticed by a human eye – see persistence of vision and flicker fusion threshold.Macula of retina: The macula or macula lutea (from Latin macula, "spot" + lutea, "yellow") is an oval-shaped pigmented area near the center of the retina of the human eye. It has a diameter of around .Orthoptics: Orthoptics is a profession allied to medicine whose primary remit is the diagnosis and non-medical management of strabismus (squint), amblyopia (lazy eye) and eye movement disorders. International Orthoptic Association document "professional role" The word orthoptics comes from the Greek words ὀρθός orthos, "straight" and ὀπτικός optikοs, "relating to sight" and much of the practice of orthoptists concerns refraction and muscular eye control.Tadpole pupil: The eye is made up of the sclera, the iris, and the pupil, a black hole located at the center of the eye with the main function of allowing light to pass to the retina. Due to certain muscle spasms in the eye, the pupil can resemble a tadpole, which consists of a circular body, no arms or legs, and a tail.Binocular vision: Binocular vision is vision in which creatures having two eyes use them together. The word binocular comes from two Latin roots, bini for double, and oculus for eye.Farnsworth Lantern Test: The Farnsworth Lantern Test, or FALANT, is a test of color vision originally developed specifically to screen sailors for shipboard tasks requiring color vision, such as identifying signal lights at night. It screens for red-green deficiencies, but not the much rarer blue color deficiency.Sustainability marketing myopia: Sustainability marketing myopia is a term used in sustainability marketing referring to a distortion stemming from the overlooking of socio-environmental attributes of a sustainable product or service at the expenses of customer benefits and values. The idea of sustainability marketing myopia is rooted into conventional marketing myopia theory, as well as green marketing myopia.StrabismusIntraocular lens power calculation: The aim of an accurate intraocular lens power calculation is to provide an intraocular lens (IOL) that fits the specific needs and desires of the individual patient. The development of better instrumentation for measuring the eye's axial length (AL) and the use of more precise mathematical formulas to perform the appropriate calculations have significantly improved the accuracy with which the surgeon determines the IOL power.Congenital cataractLow vision assessment: Low vision is both a subspeciality and a condition. Optometrists and Ophthalmologists after their training may undergo further training in Low vision assessment and management.Plaque-forming unit: In virology, a plaque-forming unit (PFU) is a measure of the number of particles capable of forming plaques per unit volume, such as virus particles. It is a functional measurement rather than a measurement of the absolute quantity of particles: viral particles that are defective or which fail to infect their target cell will not produce a plaque and thus will not be counted.Avo PhotonicsOptokinetic reflexRimless eyeglasses: Rimless eyeglasses, are a type of eyeglasses in which the lenses are mounted directly to the bridge and/or temples. The style is divided into two subtypes: three piece glasses are composed of lenses mounted to a bridge and two separate temple arms, while rimways (also called cortlands) feature a supporting arch that connects the temples to the bridge and provides extra stability for the lenses.Retinal regeneration: Retinal regeneration deals with restoring retinal function to vertebrates so impaired.Diffuse lamellar keratitis: Diffuse lamellar keratitis (DLK) is a sterile inflammation of the cornea which may occur after refractive surgery, such as LASIK. Its incidence has been estimated to be 1 in 500 patients, though this may be as high as 32% in some cases.Hemispatial neglectScotomaOptic neuritisCanon EOS 5Plastic headlight restorationAutorefractor: An autorefractor or automated refractor is a computer-controlled machine used during an eye examination to provide an objective measurement of a person's refractive error and prescription for glasses or contact lenses. This is achieved by measuring how light is changed as it enters a person's eye.Spasm of accommodation: A spasm of accommodation (also known as an accommodation, or accommodative spasm) is a condition in which the ciliary muscle of the eye remains in a constant state of contraction. Normal accommodation allows the eye to "accommodate" for near-vision.Biological motion: Biological motion is a term used by social and cognitive neuroscientists to refer to the unique visual phenomenon of a moving, animate object. Often, the stimuli used in biological motion experiments are just a few moving dots that reflect the motion of some key joints of the moving organism.Grow lightAge-Related Eye Disease Study: The Age-Related Eye Disease Study (AREDS) was a clinical trial sponsored by the National Eye Institute, one of the National Institutes of Health in the United States.A Randomized, Placebo-Controlled, Clinical Trial of High-Dose Supplementation With Vitamins C and E, Beta Carotene, and Zinc for Age-Related Macular Degeneration and Vision Loss.Charles D. Phelps: Charles Dexter Phelps (September 16, 1937 – September 13, 1985) was a prominent American medical doctor, professor, and researcher in the field of ophthalmology. The clinical studies he oversaw contributed to significant advances in the scientific understanding and surgical and pharmacological treatment of glaucoma.Dyslexia: (developmental),Stereopsis: Stereopsis (from the Greek στερεο- [meaning "solid", and ὄψις] opsis, "appearance, [[visual perception|sight") is a term that is most often used to refer to the perception of depth and 3-dimensional structure obtained on the basis of visual information deriving from two eyes by individuals with normally developed binocular vision.Red reflex: The red reflex refers to the reddish-orange reflection of light from the eye's retina that is observed when using an ophthalmoscope or retinoscope from approximately 30 cm / 1 foot. This examination is usually performed in a dimly lit or dark room.AnisometropiaFluspirilenePhotometry (astronomy): Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation. When photometry is performed over broad wavelength bands of radiation, where not only the amount of radiation but also its spectral distribution is measured, the term spectrophotometry is used.Astigmatism: An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different focus. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances.Photopic vision: Photopic vision is the vision of the eye under well-lit conditions. In humans and many other animals, photopic vision allows color perception, mediated by cone cells, and a significantly higher visual acuity and temporal resolution than available with scotopic vision.Fairness to Contact Lens Consumers Act: The Fairness to Contact Lens Consumers Act (, 117 Stat. 2025, 2026, 2027, 2028 and 2029, codified at et seq.Cats in the United States: Many different species of mammal can be classified as cats (felids) in the United States. These include domestic cat (both house cats and feral), of the species Felis catus; medium-sized wild cats from the genus Lynx; and big cats from the genera Puma and Panthera.Psychophysiology: Psychophysiology (from Greek , psȳkhē, "breath, life, soul"; , physis, "nature, origin"; and , [is the branch of psychology] that is concerned with the [[physiology|physiological bases of psychological processes. While psychophysiology was a general broad field of research in the 1960s and 1970s, it has now become quite specialized, and has branched into subspecializations such as social psychophysiology, cardiovascular psychophysiology, cognitive psychophysiology, and cognitive neuroscience.Cataract surgerySubatomic scale: The subatomic scale is the domain of physical size that encompasses objects smaller than an atom. It is the scale at which the atomic constituents, such as the nucleus containing protons and neutrons, and the electrons, which orbit in spherical or elliptical paths around the nucleus, become apparent.Argon–argon dating: Argon–argon (or 40Ar/39Ar) dating is a radiometric dating method invented to supersede potassium-argon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses a single measurement of argon isotopes.Tema Motorway: The Tema Motorway is a highway that links Tema to Accra—capital of Ghana. It was the only motorway in Ghana.Blue colour works: A blue colour works () is a paintworks where blue paint for use in glassmaking is produced. Usually the pigment, cobalt blue, needed for this purpose, was manufactured from cobalt-containing ore as in the case of the factories listed below.Buckhorn Island State ParkPresbyopiaGeneralizability theory: Generalizability theory, or G Theory, is a statistical framework for conceptualizing, investigating, and designing reliable observations. It is used to determine the reliability (i.Avi Wallerstein: Avi Wallerstein is a Canadian laser eye surgeon who practices in Montreal and Toronto. In 2001, he and Mark Cohen founded LASIK MD, Canada's largest provider of laser refractive surgery.Temporal analysis of products: Temporal Analysis of Products (TAP), (TAP-2), (TAP-3) is an experimental technique for studyingPurtscher's retinopathy: Purtscher's retinopathy is a disease where part of the eye (retina) is damaged. Usually associated with severe head injuries, it may also occur with other types of trauma, such as long bone fractures, or with several non-traumatic systemic diseases.Diabetic retinopathy: ( )Spalding MethodHalogen dance rearrangement: The halogen dance rearrangement is an organic reaction in which a halogen substituent moves to a new position on an aromatic ring system. The reaction belongs to a class of organic reactions called 1,2-rearrangements.

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

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)

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

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)

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

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)

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

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)

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

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)

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

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)

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

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)

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

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)



spatial frequency

  • In addition, quantal noise is used to study the effect of grating area and spatial frequency on contrast sensitivity resulting in the extension of the new contrast detection model describing the human contrast detection system as a simple image processor. (bl.uk)
  • The tests are sinusoidal gratings whose parameters (luminance, contrast, spatial frequency) are controlled by the computer. (metrovision.fr)
  • The results of the exam are represented as a curve (here in red) giving the contrast sensitivity versus spatial frequency. (metrovision.fr)
  • The highest spatial frequency perceived at maximum contrast is around 30 to 45 cycles per degree. (metrovision.fr)
  • Our results suggest that cascading (multiplying the contrast of the instrumental MTF with the unaided CSF at each spatial frequency) is useful for predicting visually aided CSFs to within 4 dB. (osapublishing.org)
  • The stability of this environment is maintained during saccadic and vergence eye movements due to reduced contrast sensitivity to low spatial frequency information. (arvojournals.org)
  • Our recent work has revealed a new type of selective reduction of contrast sensitivity to high spatial frequency patterns during the fast phase of dynamic accommodation responses compared with steady-state accommodation. (arvojournals.org)

signal probability and relevance

  • Here, we reassessed the prior influences of signal probability and relevance on visual contrast detection using a reverse-correlation technique that quantifies how signal-like fluctuations in noise predict trial-to-trial variability in choice discarded by conventional analyses. (ox.ac.uk)
  • We found that signal probability and relevance both increased energy sensitivity, but in dissociable ways. (ox.ac.uk)

wavefront

  • Because their wavefront aberrations may be altered by the optics of the eye, especially by accommodation, some researchers question the ability of their modulation transfer functions (MTF) to predict changes in contrast sensitivity functions (CSF) through them. (osapublishing.org)

ocular

  • According to the model the human contrast detection system comprises low-pass filtering due to ocular optics, addition of light dependent noise at the event of quantal absorption, high-pass filtering due to the neural visual pathways, addition of internal neural noise, after which detection takes place by a local matched filter, whose sampling efficiency decreases as grating area is increased. (bl.uk)
  • The evaluation of the contrast sensitivity function presents much more sensitivity than the "standard" visual acuity measurements in alterations of ocular media transparency and diseases of the retina and the optic nerve. (metrovision.fr)
  • The results were accounted for by a contrast gain control model of a cortical mechanism for contrast detection during dynamic ocular accommodation. (arvojournals.org)

LASIK

  • Evaluate visual outcomes and contrast sensitivity for subjects undergoing bilateral myopic LASIK with a Nexisvision Shield or bandage contact lens placed postoperatively. (clinicaltrials.gov)
  • Change in contrast sensitivity compared to baseline will be documented at specific time intervals beginning immediately after LASIK surgery. (clinicaltrials.gov)
  • Historically, LASIK has been reported to decrease contrast sensitivity post operatively and patients have been advised to take the day off of work and potentially the day after LASIK. (clinicaltrials.gov)

measurements

  • You may display graphs of the mean photopic and mesopic contrast sensitivity in a logMar scale base on measurements with the Vector Vision CSV 1000 ( www.vectorvision.com ). (datagraph-med.net)
  • The choice of eye care professionals, occupational testers, and clinical researchers around the globe, for accurate, convenient and rapidly-administered contrast sensitivity measurements. (marsperceptrix.com)

baseline

  • Cues predicting the relevant location increased primarily the sensitivity of true positives by suppressing internal noise during signal processing, whereas cues predicting greater signal probability increased both the frequency and the sensitivity of false positives by biasing the baseline activity of signal-selective units. (ox.ac.uk)

decrease

  • It is well known that refractive surgery causes a temporary mild decrease in contrast sensitivity immediately after surgery. (rochester.edu)

test

  • During the pre-operative evaluation we'll test your contrast sensitivity with a special eye chart that has light gray letters on the bright background. (rochester.edu)
  • During your pre-operative evaluation at Flaum Eye Institute Refractive Surgery Center, we'll carefully measure your pupil size, analyze the subtle optics of your visual system and test your contrast sensitivity with a special eye chart that has light gray letters on the bright background. (rochester.edu)
  • Twenty-three bilaterally pseudophakic patients with a conventional IOL (AcrySof SA60AT) and a blue light-filtering IOL (AcrySof Natural SN60AT) were tested for intraindividual comparison of visual acuity (ETDRS chart), color perception (Farnsworth-Munsell 100-Hue test), and contrast sensitivity with and without glare (Contrast Sensitivity Pattern Generator). (uzh.ch)
  • Starting from Version 4.07 Datagraph med supports the HACSS contrast sensitivity test. (datagraph-med.net)
  • Each chart is printed with 48 different contrast levels, declining gradually in 0.04 log unit steps - the finest steps available in any printed contrast test. (marsperceptrix.com)
  • To test the sensitivity of a microscope in distinguishing variations of optical thickness in an object, it is useful to have test materials somewhat analogous to the diatoms normally used to test lateral resolving power. (osapublishing.org)

visual

  • Many of the visual problems that you hear about as being negatives with regard to refractive surgery are related to changes in contrast sensitivity. (rochester.edu)
  • Unlike other contrast tests that assess visual acuity using low contrast targets, the Mars tests are true contrast sensitivity tests that assess the lowest contrasts your patients can perceive, rather than the smallest letters they can identify at some low, arbitrarily chosen contrast. (marsperceptrix.com)

losses

  • Certain factors can result in more persistent losses in contrast sensitivity. (rochester.edu)

influences

  • We then measured the influences of microsaccades on contrast sensitivity in a 2AFC experiment in which subjects reported the orientation (±45°) of a Gabor stimulus at either 0.8 or 10 cycles/deg. (arvojournals.org)

perception

  • To investigate color perception and contrast sensitivity with and without additional glare in pseudophakic patients with a conventional intraocular lens (IOL) in one eye and a blue light-filtering IOL in the fellow eye. (uzh.ch)
  • Despite some subjective difference in color and contrast perception in a minority of patients, the study did not show significantly different results for the two IOL types. (uzh.ch)

high

  • Contrast can be "high" like a black dog in a snowy field on a sunny day or the standard Snellen Chart or it can be low, like a white rabbit in that same snowy field or a person wearing a dark coat walking along the side of the road at dusk. (rochester.edu)
  • When participants in Group A were told that men were more likely to have high levels of "contrast-sensitivity ability," women assessed their contrast-sensitivity ability lower than men did. (blogspot.com)
  • In the same fictitious skill of "contrast sensitivity," students were asked, "How high would you have to score to be convinced that you have high ability in this task? (blogspot.com)
  • Nonlinear and nonmonotonic behavior of the experimental observables is discussed theoretically with a view to high resolution, enhanced contrast, and minimally invasive mapping. (upc.edu)

detect

  • In its most basic terms, contract sensitivity describes our ability to detect subtle differences between objects that are not black and white. (rochester.edu)
  • Our ability to detect contrast is best when there is very bright lighting and it decreases as the light becomes dimmer. (rochester.edu)
  • The use of contrast sensitivity testing by the Flaum Eye Institute Refractive Surgery Center team allows us to detect subtle nuances about your vision, making refractive surgery safer for our patients. (rochester.edu)
  • Dr. Correll describes this fictitious ability to detect correct proportions of black and white as "contrast-sensitivity ability. (blogspot.com)

changes

  • Here were report data which show a strong correlation between the effects of reduced contrast sensitivity during dynamic accommodation and velocity of accommodation responses, elicited by ramp changes in accommodative demand. (arvojournals.org)
  • Sensitivity, however, was not altered during attempted accommodation responses in the absence of crystalline-lens changes due to cycloplegia. (arvojournals.org)
  • This approach allowed us to estimate separately the sensitivity of true and false positives to parametric changes in signal energy. (ox.ac.uk)

however

  • Contrast sensitivity testing, however, showed similar curves for the two IOL types with and without additional glare. (uzh.ch)
  • However, conventional analyses that estimate sensitivity and bias by comparing true- and false-positive rates offer limited insights into the mechanisms responsible for these effects. (ox.ac.uk)

cycles

  • No benefit of microsaccades on contrast sensitivity was observed with a 10 cycles/deg grating. (arvojournals.org)

patients

  • Regarding contrast sensitivity, 5 patients (21.7%) indicated noticeable difference between the two eyes. (uzh.ch)

noise

  • Fractions of meV of energy dissipation are shown to provide contrast above the noise level. (upc.edu)

vision

  • Contrast sensitivity is a better measure of "quality" or crispness of vision. (rochester.edu)
  • The dashed lines represent the normal range for photopic contrast sensitivity for a younger population between 20 and 50 years of age as given by vector vision inc. (datagraph-med.net)

suggest

  • These findings suggest that contrast sensitivity reduction during dynamic accommodation may be a consequence of cortical inhibition driven by proprioceptive-like signals originating within the ciliary muscle, rather than by corollary discharge signals elicited simultaneously with the motor command to the ciliary muscle. (arvojournals.org)

chart

  • With the Mars tests, it is the contrast, and not the letter (or numeral) size, which diminishes from the beginning to the end of the chart. (marsperceptrix.com)

rather

  • 1 With such a "phase-wedge," a commercial phase-contrast objective shows a path difference of 80 A with rather good contrast. (osapublishing.org)

results

  • In sum, our theoretical and experimental results show that, even though microsaccadic transients slightly improve sensitivity to low spatial frequencies, observers do not normally take advantage of them. (arvojournals.org)

range

  • Most of our world falls in the medium to low contrast range. (rochester.edu)

show

  • We show that, in agreement with theoretical predictions, contrast sensitivity slightly improved in the trials with one or more microsaccades compared to drift-only trials. (arvojournals.org)
  • We show how the tip can be made to oscillate in the proximity of the surface and in perpetual contact with the adsorbed water layers while the second mode amplitude and phase provide enhanced contrast and sensitivity. (upc.edu)
  • The phase-contrast method has a disadvantage in that in an object any detail of homogeneous thickness will show an uneven brightness. (osapublishing.org)