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By the 10th Revision of the [[World Health Organization|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.[http://www3.who.int/icd/currentversion/fr-icd.htm][http://www.who.int/mediacentre/factsheets/fs282/en/] | By the 10th Revision of the [[World Health Organization|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.[http://www3.who.int/icd/currentversion/fr-icd.htm][http://www.who.int/mediacentre/factsheets/fs282/en/] | ||
==Legal Blindness== | |||
In 1934, the [[American Medical Association]] adopted the following definition of blindness: | |||
:''"Central visual acuity of 20/200 or less in the better eye with corrective glasses or central visual acuity of more than 20/200 if there is a visual field defect in which the peripheral field is contracted to such an extent that the widest diameter of the visual field subtends an angular distance no greater than 20 degrees in the better eye."''<ref name="Koestler">Koestler, F. A., (1976). ''The unseen minority: a social history of blindness in the United States.'' New York: David McKay.</ref> | |||
The [[United States Congress]] included this definition as part of the [[Aid to the Blind]] program in the [[Social Security Act]] passed in 1935<ref name="Koestler"/><ref name="Corn">Corn, AL; Spungin, SJ. [http://www.coe.ufl.edu/copsse/docs/IB-10/1/IB-10.pdf "Free and Appropriate Public Education and the Personnel Crisis for Students with Visual Impairments and Blindness."] Center on Personnel Studies in Special Education. April 2003.</ref>. In 1972, the Aid to the Blind program and two others combined under Title XVI of the Social Security Act to form the [[Supplemental Security Income]] program[http://www.ssa.gov/history/pdf/80chap12.pdf] which currently states: | |||
:''"An individual shall be considered to be blind for purposes of this title if he has central visual acuity of 20/200 or less in the better eye with the use of a correcting lens. An eye which is accompanied by a limitation in the fields of vision such that the widest diameter of the visual field subtends an angle no greater than 20 degrees shall be considered for purposes of the first sentence of this subsection as having a central visual acuity of 20/200 or less. An individual shall also be considered to be blind for purposes of this title if he is blind as defined under a State plan approved under title X or XVI as in effect for October 1972 and received aid under such plan (on the basis of blindness) for December 1973, so long as he is continuously blind as so defined."'' <ref>Social Security Act. [http://www.ssa.gov/OP_Home/ssact/title16b/1614.htm "Sec. 1614. Meaning of terms."] Retrieved Feb 17, 2006.</ref> | |||
[[Kuwait]] is one of many nations that share the same criteria for legal blindness<ref name="Al-Merjan">Al-Merjan JI, Pandova MG, Al-Ghanim M, Al-Wayel A, Al-Mutairi S. "Registered blindness and low vision in Kuwait." ''Ophthalmic Epidemiol.'' 2005 Aug;12(4):251-7. PMID 16033746.</ref>. | |||
==Cultural Aspect== | |||
The story of the [[Blind Men and an Elephant]] uses blindness as a symbol of limited perception and perspective. Stories such as ''[[The Cricket on the Hearth]]'' by [[Charles Dickens]] provided yet another view of blindness, wherein those affected by it were ignorant of their surroundings and easily deceived. [[H. G. Wells]]' story [[The Country of the Blind]] explores what would happen if a sighted man found himself trapped in a country of blind people to emphasise societies atttitude to blind people by turning the situation on its head. | |||
The authors of modern educational materials (see: [[blindness and education]] for further reading on that subject), as well as those treating [[blindness in literature]], have worked to paint a different picture of blind people as three-dimensional individuals with a range of abilities, talents, and even character flaws. | |||
The [[Moche]] people of ancient [[Peru]] depicted the blind in their ceramics. <ref>Berrin, Katherine & Larco Museum. ''The Spirit of Ancient Peru:Treasures from the [[Larco Museum|Museo Arqueológico Rafael Larco Herrera]].'' New York: [[Thames and Hudson]], 1997.</ref> | |||
Statements that this or that species of [[mammal]]s are "born blind" refers to them being born with their eyes closed and their eyelids fused together; the eyes open later. One example is the [[rabbit]]. | |||
In humans the eyelids are fused for a while before birth, but open again before the normal birth time, but very premature babies are sometimes born with their eyes fused shut, and opening later. | |||
==References== | ==References== | ||
Revision as of 04:45, 30 April 2013
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saumya Easaw, M.B.B.S.[2]
Overview
Blindness is the condition of lacking visual perception due to physiological or neurological factors.
Various scales have been developed to describe the extent of vision loss and define "blindness."[1] Total blindness is the complete lack of form and light perception and is clinically recorded as "NLP," an abbreviation for "no light perception."[1] Blindness is frequently used to describe severe visual impairment with residual vision. Those described as having only "light perception" can see no more than the ability to tell light from dark. A person with only "light projection" can tell the general direction of a light source.
In order to determine which people may need special assistance because of their visual disabilities, various governmental jurisdictions have formulated more complex definitions referred to as legal blindness.[2] 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 (6 m) from an object to see it with the same degree of clarity as a normally sighted person could from 200 feet (60 m). 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, have no vision. The rest have some vision, from light perception alone to relatively good acuity. Low vision is sometimes used to describe visual acuities from 20/70 to 20/200. [3]
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.[4][5]
Legal Blindness
In 1934, the American Medical Association adopted the following definition of blindness:
- "Central visual acuity of 20/200 or less in the better eye with corrective glasses or central visual acuity of more than 20/200 if there is a visual field defect in which the peripheral field is contracted to such an extent that the widest diameter of the visual field subtends an angular distance no greater than 20 degrees in the better eye."[3]
The United States Congress included this definition as part of the Aid to the Blind program in the Social Security Act passed in 1935[3][4]. In 1972, the Aid to the Blind program and two others combined under Title XVI of the Social Security Act to form the Supplemental Security Income program[6] which currently states:
- "An individual shall be considered to be blind for purposes of this title if he has central visual acuity of 20/200 or less in the better eye with the use of a correcting lens. An eye which is accompanied by a limitation in the fields of vision such that the widest diameter of the visual field subtends an angle no greater than 20 degrees shall be considered for purposes of the first sentence of this subsection as having a central visual acuity of 20/200 or less. An individual shall also be considered to be blind for purposes of this title if he is blind as defined under a State plan approved under title X or XVI as in effect for October 1972 and received aid under such plan (on the basis of blindness) for December 1973, so long as he is continuously blind as so defined." [5]
Kuwait is one of many nations that share the same criteria for legal blindness[6].
Cultural Aspect
The story of the Blind Men and an Elephant uses blindness as a symbol of limited perception and perspective. Stories such as The Cricket on the Hearth by Charles Dickens provided yet another view of blindness, wherein those affected by it were ignorant of their surroundings and easily deceived. H. G. Wells' story The Country of the Blind explores what would happen if a sighted man found himself trapped in a country of blind people to emphasise societies atttitude to blind people by turning the situation on its head.
The authors of modern educational materials (see: blindness and education for further reading on that subject), as well as those treating blindness in literature, have worked to paint a different picture of blind people as three-dimensional individuals with a range of abilities, talents, and even character flaws.
The Moche people of ancient Peru depicted the blind in their ceramics. [7]
Statements that this or that species of mammals are "born blind" refers to them being born with their eyes closed and their eyelids fused together; the eyes open later. One example is the rabbit.
In humans the eyelids are fused for a while before birth, but open again before the normal birth time, but very premature babies are sometimes born with their eyes fused shut, and opening later.
References
- ↑ 1.0 1.1 International Council of Ophthalmology. "International Standards: Visual Standards — Aspects and Ranges of Vision Loss with Emphasis on Population Surveys." April 2002.
- ↑ Belote, Larry. "Low Vision Education and Training: Defining the Boundaries of Low Vision Patients." A Personal Guide to the VA Visual Impairment Services Program. Retrieved March 31, 2006.
- ↑ 3.0 3.1 Koestler, F. A., (1976). The unseen minority: a social history of blindness in the United States. New York: David McKay.
- ↑ Corn, AL; Spungin, SJ. "Free and Appropriate Public Education and the Personnel Crisis for Students with Visual Impairments and Blindness." Center on Personnel Studies in Special Education. April 2003.
- ↑ Social Security Act. "Sec. 1614. Meaning of terms." Retrieved Feb 17, 2006.
- ↑ Al-Merjan JI, Pandova MG, Al-Ghanim M, Al-Wayel A, Al-Mutairi S. "Registered blindness and low vision in Kuwait." Ophthalmic Epidemiol. 2005 Aug;12(4):251-7. PMID 16033746.
- ↑ Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997.