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lack or loss of ability to see (see vision). Legally, blindness is defined as less than 20/200 vision in the better eye with glasses (vision of 20/200 is the ability to see at 20 feet only what the normal eye can see at 200 feet). A person with 20° or less vision (pinhole vision) is also legally blind. In 2002, the number of people classified as legally blind in the United States was estimated at 10 million; millions more had severe visual impairments. The five leading causes of impaired vision and blindness in the United States are age-related macular degeneration, cataract, glaucoma, diabetic retinopathy, and atrophy of the optic nerve. Besides health care problems, issues related to employment, independent living, and literacy should all be considered when caring for patients who are blind. The American Foundation for the Blind is a resource center for information related to visual problems. They can be contacted by calling 1-800-232-5463 or consulting their web site at http://www.afb.org.
blue blindness (blue-yellow blindness) popular names for imperfect perception of blue and yellow tints; see tritanopia and tetartanopia.
color blindness color vision deficiency.
complete color blindness monochromatic vision.
day blindness hemeralopia.
legal blindness that defined by law, usually, maximal visual acuity in the better eye after correction of 20/200 with a total diameter of the visual field in that eye of 20°.
night blindness see night blindness.
object blindness (psychic blindness) visual agnosia.
red blindness popular name for protanopia.
red-green blindness (red-green color blindness) popular names for any imperfect perception of red and green tints, including all the most common types of color vision deficiency. See deuteranomaly, deuteranopia, protanomaly, and protanopia.
snow blindness dimness of vision, usually temporary, due to the glare of the sun upon snow.
total color blindness monochromatic vision.
yellow blindness popular name for tritanopia.
visual agnosia for objects, in which objects are seen but not identified; caused by a lesion in Brodmann area 18 of the occipital cortex.
Sight without recognition due to a brain lesion.
See also: blindness