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Blindness can be defined physiologically as the condition of
lacking visual perception. The definition as it applies to people
thus legally classified is, however, more complex.
"Blindness" also applies to partial visual impairment:
In North America and most of Europe, legal blindness is defined
as visual acuity (vision) of 20/200 (6/60) or less in the better
eye with best correction possible. This means that a legally blind
individual would have to stand 20 feet from an object to see it
with the same degree of clarity as a normally sighted person could
from 200 feet. In many areas, people with average acuity who nonetheless
have a visual field of less than 20 degrees (the norm being 180
degrees) are also classified as being legally blind.
Approximately ten percent of those deemed legally blind, by any
measure, are fully sightless. The rest have some vision, from
light perception alone to relatively good acuity. Those who are
not legally blind, but nonetheless have serious visual impairments,
possess low vision.
By the 10th Revision of the WHO International Statistical Classification
of Diseases, Injuries and Causes of Death, low vision is defined
as visual acuity of less than 6/18, but equal to or better than
3/60, or corresponding visual field loss to less than 20 degrees,
in the better eye with best possible correction. Blindness is
defined as visual acuity of less than 3/60, or corresponding visual
field loss to less than 10 degrees, in the better eye with best
possible correction. Visual impairment includes low vision as
well as blindness. |
Blind Information: Inside
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Causes ] [ Adaptive Techniques ] [ Tools ]
[
Social Attitude towards Blindness ] [ Articles ] [ Organizations ]
[ Support Services ] [ Special Education Schools ] [ Camps ]
[ Books ] [ Videos ] [ Magazines ] [ Products ] [ Software ]
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