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blindness,partial or complete loss of sight. Blindness may be caused by injury, by lesions of the brain or optic nerve, by disease of the cornea or retina, by pathological changes originating in systemic disorders (e.g., diabetesdiabetes
or diabetes mellitus
, chronic disorder of glucose (sugar) metabolism caused by inadequate production or use of insulin, a hormone produced in specialized cells (beta cells in the islets of Langerhans) in the pancreas that allows the body to use and store
..... Click the link for more information. ) and by cataractcataract,
in medicine, opacity of the lens of the eye, which impairs vision. In the young, cataracts are generally congenital or hereditary; later they are usually the result of degenerative changes brought on by aging or systemic disease (diabetes).
..... Click the link for more information. , glaucomaglaucoma
, ocular disorder characterized by pressure within the eyeball caused by an excessive amount of aqueous humor (the fluid substance filling the eyeball). This causes pressure against the optic nerve and compression of the blood vessels of the eye—the resulting
..... Click the link for more information. , or retinal detachment. Blindness caused by infectious diseases, such as trachomatrachoma
, infection of the mucous membrane of the eyelids caused by the bacterium Chlamydia trachomatis. Trachoma infects more than 150 million people worldwide.
..... Click the link for more information. , and by dietary deficiencies is common in underdeveloped countries where medical care is inadequate. River blindness, caused by a parasitic worm transmitted by black flies, results in severe itching and disfiguring lesions. Infection of the eye area can destroy vision. An estimated 18 million people in Africa, Latin America, South America, and Yemen are infected with the parasite; 1 million of those infected are expected to become blind or severely impaired. Until recently, pesticides have been used to eradicate the flies. Two new drugs, ivermectin and amocarzine, have proved effective when used together. Most infectious diseases of the eye can be prevented or cured.
A major cause of congenital blindness in the United States, ophthalmia neonatorum, which is caused by gonorrhea organisms in the maternal birth canal, is now prevented by placing silver nitrate solution in all newborn infants' eyes. Retinitis pigmentosis, a hereditary and degenerative eye disease, affects 100,000 people in the United States. An early sign is night blindness which progresses to total blindness. Color blindnesscolor blindness,
visual defect resulting in the inability to distinguish colors. About 8% of men and 0.5% of women experience some difficulty in color perception. Color blindness is usually an inherited sex-linked characteristic, transmitted through, but recessive in, females.
..... Click the link for more information. , an hereditary problem, is an inability to distinguish colors, most commonly red and green. Snow blindness is a temporary condition resulting from a burn of the cornea caused by the reflection of sunlight on snow. Night blindness results from a deficiency of vitamin A. See eyeeye,
organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of eye are the simple eye, found in many invertebrates, and the compound eye, found in insects and many other
..... Click the link for more information. .
in the strictly scientific sense, the permanent and irreversible loss of vision in both eyes, the inability to distinguish light from darkness. In cases of total blindness visual acuity is equal to 0.
In the practical and social sense, blindness has a much broader definition. A person is considered to be blind when he cannot see well enough to orient himself in his surroundings or get around outside his home without help. A blind person may be photoreceptive, that is, able to distinguish light and the direction it is coming from, and may be able to see the outlines of large objects. The legally blind include persons who are practically sightless, possessing extremely low visual acuity (to 0.02). An individual who does not see well enough to work even when wearing glasses is said to be industrially blind. A person whose vision has deteriorated to the point that he cannot do his customary work is considered occupationally blind. For example, individuals engaged in intellectual work are said to be occupationally blind when they can no longer see well enough to read.
According to the World Health Organization (WHO), there were 10 to 15 million blind persons in the world in 1972. The main causes of blindness are glaucoma, trachoma, and traumatism of the eyes. The causes of blindness and the number of blind persons vary from country to country. For example, pox diseases caused many cases of blindness in prerevolutionary Russia, whereas no such incidences have been reported in the USSR. In economically developed countries blindness is primarily caused by progressive myopia, traumatism, or vascular lesions of the retina, including those produced by diabetes mellitus. In developing countries infectious and parasitic diseases are the main causes of blindness. Of the approximately 500 million persons with trachoma, approximately 2 million are blind. The disease is widespread in Asia, Africa, and Latin America. Prior to the October Revolution of 1917,21.5 percent of all incidences of blindness were caused by trachoma. By 1968 trachoma had been eradicated as a major disease in the USSR. In industrial countries, where occupational injuries are fairly common, most of the blind are men.
Blindness can be controlled by preventing certain eye injuries and diseases. In the USSR, for example, glaucoma is diagnosed early, and those suffering from the disease have regular checkups. Recent advances in eye surgery have restored some degree of vision to many blind persons.
The All-Russian Society for the Blind was organized in 1925; similar societies have been organized in other Union republics. A network of specialized secondary and eight-year schools has been established for the education of children who are blind or have poor eyesight. Textbooks, literary works, and magazines are published in Braille. Special sound-recording studios and record and tape libraries have been established.
Blind adolescents and adults receive occupational training at special industrial enterprises organized by societies for the blind. After finishing their studies they may work at these enterprises or at enterprises in other localities.
In capitalist countries philanthropic societies are the chief organizations involved in finding work for the blind. The World Council for the Welfare of the Blind, which works in cooperation with UNESCO and other agencies of the UN, was established in Paris in 1951.
REFERENCESGolovin, S. S. O slepote v Rossii. Odessa, 1910.
Averbakh, M. I. “Uchenie o slepote, ocherk 1.” In his book Oftal’mologicheskie ocherki. Moscow, 1949.
Mnogotomnoe rukovodstvo po glaznym bolezniam, vol. 1, book 2. Edited by V. N. Arkhangel’skii. Moscow, 1962.
Shoev, F. I. Vserossiiskoe obshchestvo slepykh i ego deiatel’nost’. Moscow, 1965.
What does it mean when you dream about blindness?
Dreams about being blind or dreams in which someone else is blind only rarely indicate the state of physical blindness. As a dream symbol, blindness represents lack of awareness, either being truly unaware of something important that is occurring in one’s life or “turning a blind eye” to something about which one does not wish to know. Also, because our culture associates blindfolds with firing squads, blindfolds may indicate the sense of carrying out an execution, or of being executed.