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.

*  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, ...

*  Contrast sensitivity measurement in evaluations in visual symptoms caused by exposure to triethylamine

Contrast sensitivity and visual acuity were measured by optotype figures at full contrast, 2.5% contrast, and 0.6% contrast. ... The contrast sensitivity of the core makers decreased significantly at both 2.5% and 0.6% contrast during the working day. In ... The contrast sensitivity of the core makers was measured on Monday and Friday of the same week both before and immediately ... The changes in contrast sensitivity were used for the analysis. The results of binocular vision and the results of the dominant ...

*  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 ...

*  A 128-128 1.5% Contrast Sensitivity 0.9% FPN 3 µs Latency 4 mW Asynchronous Frame-Free Dynamic Vision Sensor Using...

Dynamic Vision Sensors (DVS) have recently appeared as a new paradigm for vision sensing and processing. They feature unique characteristics such as contra

*  Effects of gestational length, gender, postnatal age, and birth order on visual contrast sensitivity in infants

What covariance mechanisms underlie green/red equiluminance, chromatic contrast sensitivity and luminance contrast sensitivity ... Obtaining contrast sensitivities. The dependent measures in this study were log luminance and log chromatic contrast ... Development of temporal contrast sensitivity in human infants. Vision Research. 1997;37:1747-1754. [PubMed] ... Contrast sensitivity in anisometropic amblyopia. Investigative Ophthalmology & Visual Science. 1981;21:467-476. [PubMed] ...

*  Human contrast sensitivity to visual patterns vs. model | Open-i

Human contrast sensitivity to visual patterns vs. model predictions.a, Probability distribution of the 512 possible 3×3 1-bit ... pone-0069154-g003: Human contrast sensitivity to visual patterns vs. model predictions.a, Probability distribution of the 512 ... pone-0069154-g003: Human contrast sensitivity to visual patterns vs. model predictions.a, Probability distribution of the 512 ... amongst sensitivities plotted in (f) are: Mentions: oWe then evaluated the probability distribution of the patterns in a set of ...

*  Visual Contrast Sensitivity Test - Toxicity Testing | Brant A. Larsen, D.C.

The visual contrast sensitivity (VCS) test is an excellent screening tool for toxicity. Toxins will affect the optic nerve, ... The Visual Contrast Sensitivity (VCS) test is a CONTRAST test, not an acuity test. ... Another test that I use everyday is called a Visual Contrast Sensitivity (VCS) test. ... The ability to detect contrast is part of the brain's function. Contrast is your ability to discern black from white, and also ...

*  Fishers eye doctor offers new contrast sensitivity test | CBS 4 - Indianapolis News, Weather, Traffic and Sports | WTTV

Poor contrast sensitivity often leads to complaints of poor night vision and glare. Those symptoms can help eye care ... Roark, "Showing older Americans who have a lower contrast sensitivity, measured with our test, are more likely to have wrecks, ... Fishers eye doctor offers new contrast sensitivity test. Posted 9:47 pm, June 15, 2017, by Debby Knox ... For more information on contrast sensitivity threshold or CST testing, contact Dr. Roark at the Allisonville Eye Care Center of ...

*  Infant Contrast Sensitivity: Contributions of Factors Related to Visual Experience vs. Preprogrammed Mechanisms | JOV | ARVO...

Infant Contrast Sensitivity: Contributions of Factors Related to Visual Experience vs. Preprogrammed Mechanisms ... Infant Contrast Sensitivity: Contributions of Factors Related to Visual Experience vs. Preprogrammed Mechanisms ... preprogrammed mechanisms on visual development, we have investigated how well variation in contrast sensitivity (CS) across a ... Dobkins, K. Bosworth, R. G. (2010). Infant Contrast Sensitivity: Contributions of Factors Related to Visual Experience vs. ...

*  Abnormal scanpaths in visual search correlate with contrast sensitivity deficits in schizophrenia - Nuffield Department of...

Abnormal scanpaths in visual search correlate with contrast sensitivity deficits in schizophrenia ... Abnormal scanpaths in visual search correlate with contrast sensitivity deficits in schizophrenia ...

*  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 ...

*  Directional asymmetry in contrast sensitivity during smooth pursuit eye movement depends on spatial frequency | JOV | ARVO...

... modulates visual contrast sensitivity in an asymmetric manner. For instance, Schütz et al. (2007) reported that contrast ... We measured contrast sensitivity for a spatially localized grating (Gabor patch) of 11 c/deg. The spatial window of the grating ... Directional asymmetry in contrast sensitivity during smooth pursuit eye movement depends on spatial frequency ... Directional asymmetry in contrast sensitivity during smooth pursuit eye movement depends on spatial frequency ...

*  Contrast Sensitivity With a Subretinal Prosthesis and Implications for Efficient Delivery of Visual Information | IOVS | ARVO...

The full-field measurements of contrast sensitivity we conducted do not take into account contrast improvements at higher ... Labeled lines for image blur and contrast. Cross-modal attention influences auditory contrast sensitivity: Decreasing visual ... 6, third column). Previously experimentally measured contrast sensitivity curves were used to convert the local contrast into ... Prosthetic vision exhibits reduced contrast sensitivity and dynamic range, with 65% contrast changes required to elicit ...

*  Phase 3 Intravitreous Bevacizumab and Standard Metabolic Control for Diabetic Macular Edema - A Contrast Sensitivity Pilot...

To evaluate the effects on contrast sensitivity (CS) measurements of intravitreal bevacizumab injections associated with ... Phase 3 Intravitreous Bevacizumab and Standard Metabolic Control for Diabetic Macular Edema - A Contrast Sensitivity Pilot ... Phase 3 Intravitreous Bevacizumab and Standard Metabolic Control for Diabetic Macular Edema - A Contrast Sensitivity Pilot ...

*  Rapid Simultaneous Enhancement of Visual Sensitivity and Perceived Contrast during Saccade Preparation | Journal of Neuroscience

... we simultaneously assessed the effects of saccade preparation on both contrast sensitivity and perceived contrast. ... 2000) Spatial covert attention increases contrast sensitivity across the CSF: support for signal enhancement. Vision Res 40: ... C, Individual contrast reports and PSEs. D, Average perceived contrast as a function of time relative to saccade onset. All ... Rapid Simultaneous Enhancement of Visual Sensitivity and Perceived Contrast during Saccade Preparation. Martin Rolfs and Marisa ...

*  Nanodelivery of MRI Contrast Agent Enhances Sensitivity of Detection of Lung Cancer Metastases

Contrast enhanced Contrast enhanced CT imaging of nodules for assessment of vascularity has high sensitivity, but only medium ... Pixel intensity was used to compare 1) pre-contrast to contrast enhanced images, 2) TfR targeted and non-targeted contrast, and ... Nanodelivery of MRI Contrast Agent Enhances Sensitivity of Detection of Lung Cancer Metastases. Matthew Freedman, M.D., MBA, ... the difference between baseline/pre-contrast values and post-contrast values) from the pre-contrast values is 2.6, 4.8 and 6.6 ...

*  Human Achromatic Spatial Contrast Sensitivity Measured With Transient Visual Evoked Cortical Potential: Comparison With...

... another for high contrasts. Contrast threshold was estimated by using only the low to medium contrast data. ... G.d. Souza, B.D. Gomes, C.A. Saito, L.C. L. Silveira, M. daSilvaFilho; Human Achromatic Spatial Contrast Sensitivity Measured ... Human Achromatic Spatial Contrast Sensitivity Measured With Transient Visual Evoked Cortical Potential: Comparison With ... Human Achromatic Spatial Contrast Sensitivity Measured With Transient Visual Evoked Cortical Potential: Comparison With ...

*  Influence of Pupil Diameter on the Relation between Ocular Higher-Order Aberration and Contrast Sensitivity after Laser In Situ...

From the contrast-sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. ... We tested two indices of contrast sensitivity function: contrast sensitivity (with the CSV-1000E charts; Vector Vision Co., ... contrast sensitivity was influenced by spherical-like aberration more than by comalike aberration. In contrast, in the eyes ... significantly increases higher-order wavefront aberrations of the eye 1 2 3 4 5 6 7 8 9 and reduces contrast sensitivity. 9 10 ...

*  Intersession Repeatability of Visual Acuity, Colour Vision, Contrast Sensitivity, Retinal Sensitivity Thresholds and Retinal...

Intersession Repeatability of Visual Acuity, Colour Vision, Contrast Sensitivity, Retinal Sensitivity Thresholds and Retinal ... Intersession Repeatability of Visual Acuity, Colour Vision, Contrast Sensitivity, Retinal Sensitivity Thresholds and Retinal ... contrast sensitivity 6.7 letters, mean retinal sensitivity was 3.29 db and the central 1-mm macular subfield was 16.33 µm. ... contrast sensitivity obtained by Pelli-Robson charts and mean retinal sensitivity obtained by MP1, Nidek were tested twice at ...

*  Enrichment of Macular Pigment Enhances Contrast Sensitivity in Subjects Free of Retinal Disease: Central Retinal Enrichment...

Measuring contrast sensitivity in normal subjects with OPTEC 6500: influence of age and glare. Graefes Arch Clin Exp Ophthalmol ... Contrast sensitivity at 6 cpd was the primary outcome measure (POM) of this study. Secondary outcome measures included CS at ... Contrast sensitivity at 6 cycles per degree (cpd) was the primary outcome measure (POM). Secondary outcome measures included CS ... Contrast Sensitivity and Lateral Inhibition Are Enhanced With Macular Carotenoid Supplementation. Comments on Enrichment of ...

*  Changes in Visual Function Following Optical Treatment of Astigmatism-Related Amblyopia

Contrast Sensitivity: Middle Spatial Frequency Stimuli (Figure 4). Figure 4. Mean of V-H best-corrected contrast sensitivity at ... Contrast Sensitivity: Low Spatial Frequency Stimuli (Figure 3). Figure 3. Mean best-corrected contrast sensitivity at baseline ... Contrast Sensitivity. Assessment of contrast sensitivity was conducted using a test design similar to that used to test grating ... there was a slight reduction in contrast sensitivity for the NonA group and an improvement in contrast sensitivity for the ...

*  Speed, Spatial, and Temporal Tuning of Rod and Cone Vision in Mouse

Whereas photopic contrast sensitivity is speed tuned (Fig. 2), scotopic contrast sensitivity is temporally tuned (Fig. 3). ... The contrast sensitivities of rod vision and cone vision mice do not sum linearly to produce the contrast sensitivity of rod- ... We report here that mouse contrast sensitivity has features in common with the contrast sensitivities of human, monkey, and cat ... Remarkably, in the low-frequency range, background luminance has no effect on contrast sensitivity. Contrast sensitivity ...

*  Patent US6679855 - Method and apparatus for the correction of presbyopia using high intensity ... - Google Patents

Contrast Sensitivity. The ability to perceive differences between an object and its background. ...

*  Clinical Effectiveness of Low Vision Rehabilitation in Glaucoma Patients - Full Text View -

They are intended to improve contrast sensitivity, or being able to tell light from dark (like reading gray letters on a white ... it can involve loss of contrast sensitivity, making shapes and edges hard to discern, like those of a stair edge, or person's ...

*  Search of: Myotonic Muscular Dystrophy - List Results -

Contrast Sensitivity. *Subject Satisfaction - Subjects Satisfied With Overall Eyesight Rated as 'Good' or 'Excellent'. ...

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)

Photopic Vision

  • It is known that the rod cells are more suited to scotopic vision and cone cells to photopic vision, and that they differ in their sensitivity to different wavelengths of light. (


  • To investigate effects of visual experience versus preprogrammed mechanisms on visual development, we used multiple regression analysis to determine the extent to which a variety of variables (that differ in the extent to which they are tied to visual experience) predict luminance and chromatic (red/green) contrast sensitivity (CS), which are mediated by the magnocellular (M) and parvocellular (P) subcortical pathways, respectively. (
  • The results cannot be well accounted for neither by spatial attention nor by sensitivity modulations of parvocellular and magnocellular channels. (
  • opposed by low contrast sensitivity in cells found in the parvocellular layer. (


  • Results from pharmacological studies in cats have demonstrated the role of NMDA in contrast perception of magnocellular-tuned stimuli. (


  • We found that for a range of retinal temporal frequencies tested (1.4-22.5 Hz), the observer's contrast sensitivity was substantially higher (0.1-0.25 log unit) when the grating drifted in the opposite direction of SPEM than in the same direction. (
  • Best corrected visual acuity (ETDRS letters), colour vision thresholds on Chroma test, contrast sensitivity obtained by Pelli-Robson charts and mean retinal sensitivity obtained by MP1, Nidek were tested twice at baseline, and then at 3rd and 6th month visits, using a standardized protocols. (
  • The coefficient of repeatability for ETDRS letters was 11.76 letters, protan threshold was 3.67 db, tritan threshold 5.11 db, contrast sensitivity 6.7 letters, mean retinal sensitivity was 3.29 db and the central 1-mm macular subfield was 16.33 µm. (
  • Our study sought to investigate the impact on visual function, including contrast sensitivity (CS), of supplementation with these naturally occurring carotenoids, in individuals with low retinal concentrations. (


  • Electrophysiological contrast thresholds were estimated by linear regressions fitted to data point representing P100 tVECP amplitude as a function of log contrast, extrapolated to zero amplitude. (

situ keratomileusis

  • To investigate the influence of pupil diameter on the relation between induced changes in ocular higher-order wavefront aberrations and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. (
  • Previous studies have demonstrated that laser in situ keratomileusis (LASIK) significantly increases higher-order wavefront aberrations of the eye 1 2 3 4 5 6 7 8 9 and reduces contrast sensitivity. (


  • f, Averaged sensitivity for detection of the patterns as a function of their probability, measured on three human subjects (different colors). (
  • The results were accounted for by a contrast gain control model of a cortical mechanism for contrast detection during dynamic ocular accommodation. (
  • Therefore, there is a need for enhanced sensitivity/specificity of detection for small lung cancers. (
  • Here we examine the ability of the scL-gad-d complex to increase the sensitivity of detection of lung metastases. (
  • Because of its tumor targeting specificity, deliver of an MRI contrast agent via this nanocomplex has potential for use as an agent that can identify small lung cancers, thus improving early detection and possibly increasing survival. (
  • There is evidence that schizophrenia affects perception of contrast and motion, control of eye movements, detection of visual contours, and recognition of faces or facial expressions. (
  • Parasol ganglion cells have high light/dark contrast detection, and are more sensitive at low spatial frequencies than high spatial frequencies. (
  • Spectral sensitivity is the relative efficiency of detection, of light or other signal, as a function of the frequency or wavelength of the signal. (

spatial frequencies

  • Response amplitude changed as a function of contrast differently for different spatial frequencies. (
  • At higher spatial frequencies, comprising finer and finer lines, contrast sensitivity decreases, until at about 40 cycles per degree even the brightest of bright lines and the darkest of dark lines cannot be seen. (
  • Reducing the contrast of an image reduces the visibility of these high spatial frequencies because contrast sensitivity for them is already poor. (
  • Blurring is accomplished by reducing the contrast only of the high spatial frequencies. (
  • Aerial perspective reduces the contrast of all spatial frequencies. (
  • Adults in their 70s require about three times more contrast to detect high spatial frequencies than adults in their 20s. (


  • In 215 eyes of 117 patients (age, 33.2 ± 8.3 years) undergoing LASIK for myopia of −1.25 to −13.5 D (−5.28 ± 2.55 D), ocular wavefront aberrations and contrast sensitivity function were determined before and 1 month after surgery. (
  • 9 10 11 12 13 14 15 16 17 18 19 There is a report that the induced increases in ocular higher-order aberration significantly correlated with the changes in contrast sensitivity function by LASIK. (
  • 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). (


  • Scattering adds the sky light as a veiling luminance onto the light from the object, reducing its contrast with the background sky light. (
  • That the wavelength discrimination and luminance contrast sensitivity measured in monkeys were very similar to those obtained for human observers, allowed De Valois to posit the relevance of his electrophysiological recordings in macaque monkeys to cortical processing in the early stages of the human visual system. (
  • Due to this contrast information, these cells are good at detecting changes in luminance, and thus provide useful information for performing visual search tasks and detecting edges. (


  • We estimated CSF tuning by dividing peak sensitivity by sensitivity at the lowest spatial frequency tested. (
  • Normally, peak contrast sensitivity is at about 4 cycles per degree of visual angle. (
  • It has been established that the maximum spectral sensitivity of the human eye under daylight conditions is at a wavelength of 555 nm, while at night the peak shifts to 507 nm. (
  • In other contexts, the spectral sensitivity is expressed as the relative response per light energy, rather than per quantum, normalized to a peak value of 1, and a quantum efficiency is used to calibrate the sensitivity at that peak wavelength. (


  • Change in contrast sensitivity compared to baseline will be documented at specific time intervals beginning immediately after LASIK surgery. (


  • Contrast sensitivity and visual acuity were measured by optotype figures at full contrast, 2.5% contrast, and 0.6% contrast. (
  • The Visual Contrast Sensitivity (VCS) test is a CONTRAST test, not an acuity test. (
  • The contrast threshold score represents the border between the visible and the invisible and tends to drop off much sooner than visual acuity in many disease processes. (
  • 0.001) and 10% low-contrast visual acuity ( r = 0.310, P = 0.003), but spherical-like aberrations showed no correlation with the changes in AULCSF ( r = −0.078, P = 0.485) and 10% low-contrast visual acuity ( r = 0.208, P = 0.158). (
  • By combining the information received in each eye, binocular summation can improve visual acuity, contrast sensitivity, flicker perception, and brightness perception. (
  • The ability of a person with normal visual acuity to see fine details is determined by his or her contrast sensitivity. (
  • Refractive "vision correction" surgery (especially PRK with the complication of "haze") may rarely cause a reduction in best night-time acuity due to the impairment of contrast sensitivity function (CSF) which is induced by intraocular light-scatter resulting from surgical intervention in the natural structural integrity of the cornea. (
  • The major components of the visual system can be broken up into visual acuity, depth perception, color sensitivity, and light sensitivity. (
  • One major method used to measure visual acuity during infancy is by testing an infant's sensitivity to visual details such as a set of black strip lines in a pictorial image. (


  • Contrast sensitivity has been shown to be impaired in schizophrenia. (
  • In schizophrenia, estimations of perceived contrast in surround suppression are less suppressed than for healthy adults. (

cycles per degree

  • Contrast sensitivity at 6 cycles per degree (cpd) was the primary outcome measure (POM). (


  • In sensor systems, where the output is easily quantified, the responsivity can be extended to be wavelength dependent, incorporating the spectral sensitivity. (
  • Spectral sensitivity is sometimes expressed as a quantum efficiency, that is, as probability of getting a quantum reaction, such as a captured electron, to a quantum of light, as a function of wavelength. (


  • Contrast is a feature of visual stimuli that characterizes the difference in brightness between dark and light regions of an image. (
  • Perception of contrast is affected by the temporal frequency and spatial frequency properties of a stimulus, and the sensitivity to contrast in sine wave stimuli is characterized by the Contrast sensitivity function. (


  • 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. (
  • To evaluate human achromatic spatial contrast sensitivity (CSF) with transient visual evoked cortical potential (tVECP). (


  • In order to investigate potential effects of visual experience vs. preprogrammed mechanisms on visual development, we have investigated how well variation in contrast sensitivity (CS) across a large group of typical infants (n = 182) can be accounted for by a variety of factors that differ in the extent to which they are tied to visual experience. (


  • The ability to detect contrast is part of the brain's function. (
  • For 2-10 cpd, the function showed two limbs, one for low to medium contrasts, another for high contrasts. (
  • From the contrast-sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. (
  • A person's contrast sensitivity function is contrast sensitivity as a function of spatial frequency. (
  • When a system's responsivity is a fixed monotonic nonlinear function, thatnonlinearity can be estimated and corrected for, to determine the spectral sensitivity from spectral input-output data via standard linear methods. (


  • 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. (
  • This is how a reduction of contrast can reduce the clarity of an image - by removing its fine details. (
  • A major drawback to application of the algorithm is an inherent reduction in overall image contrast produced by the operation. (


  • Here we assess concurrent changes in visual performance and perceived contrast before saccades, and show that saccade preparation enhances perception rapidly, altering early visual processing in a manner akin to increasing the physical contrast of the visual input. (


  • Evaluate visual outcomes and contrast sensitivity for subjects undergoing bilateral myopic LASIK with a Nexisvision Shield or bandage contact lens placed postoperatively. (
  • To evaluate the contrast sensitivity of a degenerate retina stimulated by a photovoltaic subretinal prosthesis, and assess the impact of low contrast sensitivity on transmission of visual information. (


  • In eyes with larger photopic pupil diameter, increases in spherical-like aberration dominantly affect contrast sensitivity, whereas in eyes with smaller pupil size, changes in comalike aberration exert greater influence on visual performance. (


  • For 0.4-0.8 cpd, response amplitude saturated at high contrast. (


  • 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. (


  • The changes in contrast sensitivity were used for the analysis. (
  • Interesting when we see people get better symptomatically and overall health, and their contrast test 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. (
  • Sensitivity, however, was not altered during attempted accommodation responses in the absence of crystalline-lens changes due to cycloplegia. (
  • Prosthetic vision exhibits reduced contrast sensitivity and dynamic range, with 65% contrast changes required to elicit responses, as compared to the 3% (OFF) to 7% (ON) changes with visible light. (


  • In the binocular measurements at2.5% contrast, sensitivity decreased in 49% of the core makers and 21% of the controls (P=0.002). (


  • We found simultaneous progressive enhancement in both orientation discrimination performance and perceived contrast as time approached saccade onset. (


  • Here we reveal this missing link by showing that saccade preparation increases the perceived signal strength-perceived contrast-consistent with enhanced neural representations of visual information at the saccade target. (
  • As the distance between an object and a viewer increases, the contrast between the object and its background decreases, and the contrast of any markings or details within the object also decreases. (


  • This agrees with the findings mentioned previously related to weaker suppression of perceived contrast in this disorder. (


  • Low contrast sensitivity and lack of OFF responses hamper delivery of visual information via a subretinal prosthesis. (
  • The responses of the rod and cone cells of the retina, however, have a very context-dependent (coupled) nonlinear response, which complicates the analysis of their spectral sensitivities from experimental data. (


  • Observers compared orientation and contrast of a test stimulus, appearing briefly before a saccade, to a standard stimulus, presented previously during a fixation period. (
  • In this study, to assess effects of saccade preparation, we asked observers to simultaneously judge both the orientation and the contrast of a test stimulus presented at the target of a cued saccadic eye movement relative to a standard stimulus shown during prior fixation ( Fig. 1 ). (
  • The perceived contrast of a stimulus is sometimes suppressed when another stimulus is presented surrounding it, an effect known as surround suppression (see Figure 1), which is similar to the simultaneous contrast illusion. (
  • In spite of these complexities, however, the conversion of light energy spectra to the effective stimulus, the excitation of the photopigment, is quite linear, and linear characterizations such as spectral sensitivity are therefore quite useful in describing many properties of color vision. (


  • Human contrast sensitivity to visual patterns vs. model predictions.a, Probability distribution of the 512 possible 3×3 1-bit pixel patterns (grey histogram). (


  • Objectives: To determine whether blurred vision caused by exposure to triethylamine (TEA) can be detected by the measurement of contrast sensitivity. (
  • Conclusions: The blurred vision caused by exposure to TEA can be documented by measuring contrast sensitivity. (
  • Poor contrast sensitivity often leads to complaints of poor night vision and glare. (
  • Our model predicts that for most visual scenes, contrast sensitivity of prosthetic vision is insufficient for triggering RGC activity by fixational eye movements. (
  • Contrast sensitivity of prosthetic vision is 10 times lower than normal, and dynamic range is two times below natural. (
  • Their sensitivity ranges overlap to provide vision throughout the visible spectrum. (
  • Scotopic vision Mesopic vision Candela Purkinje effect Photometry Photosensitive ganglion cell Adaptation (eye) Contrast (vision) Cone cell Pelz, J. (1993). (
  • Contrast vision may also be greatly reduced. (
  • For X-ray films, the spectral sensitivity is chosen to be appropriate to the phosphors that respond to X-rays, rather than being related to human vision. (


  • This asymmetry was also observed for the cut-off temporal frequencies for a grating with a contrast of 0.5. (


  • Contrast Sensitivity of the Human Eye and Its Effects on Image Quality. (


  • A practical measure of binocularity is the binocular summation ratio BSR, which is the ratio of binocular contrast sensitivity to the contrast sensitivity of the better eye. (


  • Under daylight, this either augments the contrast loss (e.g., for white objects) or opposes it (for dark objects). (


  • The contrast sensitivity of the core makers decreased significantly at both 2.5% and 0.6% contrast during the working day. (


  • Contrast threshold was estimated by using only the low to medium contrast data. (


  • The stability of this environment is maintained during saccadic and vergence eye movements due to reduced contrast sensitivity to low spatial frequency information. (


  • There are studies," said Dr. Roark, "Showing older Americans who have a lower contrast sensitivity, measured with our test, are more likely to have wrecks, car accidents. (


  • we simultaneously assessed the effects of saccade preparation on both contrast sensitivity and perceived contrast. (


  • Another test that I use everyday is called a Visual Contrast Sensitivity (VCS) test. (


  • We have also encapsulated MRI contrast agent gadopentetate dimegulamine ("gad-d") within this complex resulting in increased resolution and image intensity in a mouse model of primary cancer. (


  • Such objects have their contrasts reduced with the dark background, and their colours are shifted towards red. (


  • In photography, film and sensors are often described in terms of their spectral sensitivity, to supplement their characteristic curves that describe their responsivity. (


  • Contrast is your ability to discern black from white, and also between different shades of gray. (


  • Phase 3 Intravitreous Bevacizumab and Standard Metabolic Control for Diabetic Macular Edema - A Contrast Sensitivity Pilot Study. (


  • 2007) reported that contrast sensitivity to a 1 c/deg grating is higher when it drifts in the same direction with the SPEM than in the opposite direction. (


  • He wants to know how little contrast or how much contrast it takes for you to see real objects in the real world. (


  • In visual neuroscience, spectral sensitivity is used to describe the different characteristics of the photopigments in the rod cells and cone cells in the retina of the eye. (


  • In some cases contrast enhanced CT or MRI is used to determine the vascularity of the suspect area, although increased vascularity is not cancer specific. (


  • The contrast sensitivity of the core makers was measured on Monday and Friday of the same week both before and immediately after work and also on a third day, when air samples of TEA were collected. (