Blindness Essay, Research Paper

The term blindness implies total or

partial loss of vision involving both eyes. The exact

level of vision defined as blindness, however,

varies in different countries because of differing

legal or social requirements. In the United States,

blindness is defined as unimprovable vision of

20/200 (6/60) or worse. This means that an

individual is generally considered blind who, even

with the use of ordinary eyeglasses, can see no

better at 20 ft (6 m) than a person with normal

vision can see at 200 ft (60 m). On the other hand,

the World Health Organization (WHO) Program

Advisory Group on the Prevention of Blindness

lists the vision level suggested as blindness as a

visual acuity of less than 10/200 (3/60), which is

twice as low as the U.S. definition. The WHO

level of visual acuity is also described as the

inability to count fingers in daylight at a distance of

10 ft (3 m), because in many regions a great

number of people cannot receive formal eye

examinations but may be tested by unspecialized

personnel. From data available in the mid-1980s,

the number of persons worldwide who have a

visual acuity of less than 10/200 is estimated as 28

million. This level of handicap precludes an

individual from functioning effectively in the

community without special assistance and

rehabilitation (see BLIND, EDUCATION OF

THE). Were the definition of blindness instead

taken as 20/200, as is done in a number of

industrialized countries besides the United States,

the total number of blind persons in the world

would be about 42 million. The prevalence and

causes of blindness vary according to the

geographical location and economic status of a

region. Thus in developing countries in tropical

areas, the number of blind persons may reach at

least 21 million (using the WHO definition). This

high figure is due to the massive prevalence of

such eye diseases as TRACHOMA,

onchocerciasis (RIVER BLINDNESS), and the

NUTRITION-DEFICIENCY DISEASES

keratomalacia and xerophthalmia. In addition, few

eye doctors are present in such regions to treat

CATARACT or accidental eye injuries. In other

developing countries where eye care is not easily

available and the presence of untreated cataract

and undetected GLAUCOMA is also critical, the

number of blind persons may reach 5.5 million. In

developed countries with advanced medical

services, on the other hand, most curable

blindness is treated. Thus although many persons

may have vision problems, the exact number of

blind individuals may be less than 2 million. The

main causes of blindness in such countries are

age-related cataract, glaucoma, DIABETES, and

macular degeneration (see EYE DISEASES). In

the United States about 1 million cataracts are

removed each year and vision improved with

either an intraocular plastic lens, a contact corneal

lens, or a cataract glass. Several million Americans

are also being treated for glaucoma, which if

caught in its early stages can usually be dealt with

by medication or surgery. PAUL HENKIND,

M.D. Bibliography: Dobree, J. H., and Boulter,

Eric, Blindness and Visual Handicap: The Facts

(1982); Faye, E. E., Clinical Low Vision (1976);

Henkind, Paul, Priest, R. S., and Schiller, G.,

Compendium of Ophthalmology (1983); Kirchner,

Corinne, Data on Blindness and Visual Impairment

in the U. S. A. (1985); Koestler, Frances, The

Unseen Minority: A Social History of Blindness in

the United States (1976); Lewis, Vicky,

Development and Handicap, 3d ed. (1987);

Monbeck, Michael E., The Meaning of Blindness

(1973); Naumann, G. O., and Apple, D. J.,

Pathology of the Eye (1986); Sommer, Alfred,

Nutritional Blindness (1982); Warren, David,

Blindness and Early Development (1977); Wilson,

John, World Blindness and Its Prevention, 2 vols.

(1980-84).

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