Color Perception Tests
Type of vision test used to determine COLOR VISION DEFECTS.
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.
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)
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).
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.
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.
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.).
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.
Visually Impaired Persons
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.
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.
Diagnostic Techniques and Procedures
Anniversaries and Special Events
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)
Ocular Motility Disorders
Disorders that feature impairment of eye movements as a primary manifestation of disease. These conditions may be divided into infranuclear, nuclear, and supranuclear disorders. Diseases of the eye muscles or oculomotor cranial nerves (III, IV, and VI) are considered infranuclear. Nuclear disorders are caused by disease of the oculomotor, trochlear, or abducens nuclei in the BRAIN STEM. Supranuclear disorders are produced by dysfunction of higher order sensory and motor systems that control eye movements, including neural networks in the CEREBRAL CORTEX; BASAL GANGLIA; CEREBELLUM; and BRAIN STEM. Ocular torticollis refers to a head tilt that is caused by an ocular misalignment. Opsoclonus refers to rapid, conjugate oscillations of the eyes in multiple directions, which may occur as a parainfectious or paraneoplastic condition (e.g., OPSOCLONUS-MYOCLONUS SYNDROME). (Adams et al., Principles of Neurology, 6th ed, p240)