Canadian Medical Guide > Diseases > Nervous System Diseases > Neurologic Manifestations > Sensation Disorders > Vision Disorders Terms and Definitions

Vision Disorders

Medical Definition:	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. Visual disability refers to inability of the individual to perform specific visual tasks, such as reading, writing, orientation, or traveling unaided. (From Newell, Ophthalmology: Principles and Concepts, 7th ed, p132)
Guide Notes:	disord of vision, not dis of the eye ( = EYE DISEASES); GEN or unspecified: prefer specifics; /diag: consider also DIAGNOSTIC TECHNIQUES, OPHTHALMOLOGICAL
Also Called:	Hemeralopia,Macropsia,Metamorphopsia,Micropsia
Previously Indexed:	Vision (1966)

Vision Disorders Categories.

	Blindness - The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of EYE DISEASES; OPTIC NERVE DISEASES; OPTIC CHIASM diseases; or BRAIN DISEASES affecting the VISUAL PATHWAYS or OCCIPITAL LOBE.
	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 OPSIN genes (on X CHROMOSOME and CHROMOSOME 3, HUMAN) that code the photopigments for red, green and blue.
	Hemianopsia - Partial or complete loss of vision in one half of the visual field(s) of one or both eyes. Subtypes include altitudinal hemianopsia, characterized by a visual defect above or below the horizontal meridian of the visual field. Homonymous hemianopsia refers to a visual defect that affects both eyes equally, and occurs either to the left or right of the midline of the visual field. Binasal hemianopsia consists of loss of vision in the nasal hemifields of both eyes. Bitemporal hemianopsia is the bilateral loss of vision in the temporal fields. Quadrantanopsia refers to loss of vision in one quarter of the visual field in one or both eyes.
	Photophobia - Abnormal sensitivity to light. This may occur as a manifestation of EYE DISEASES; MIGRAINE; SUBARACHNOID HEMORRHAGE; MENINGITIS; and other disorders. Photophobia may also occur in association with DEPRESSION and other MENTAL DISORDERS.
	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.
	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.).

Vision Disorders Medical Definitions and Terms

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