Jump to content

Blindness: Difference between revisions

Page semi-protected
From Wikipedia, the free encyclopedia
Browse history interactively
← Previous edit
Content deleted Content added
VisualWikitext
→Causes: merged to visual impairment
No edit summary
Tags: Mobile edit Mobile web edit Advanced mobile edit
 
(17 intermediate revisions by 7 users not shown)
Line 1: Line 1:
#REDIRECT [[Visual impairment]]
{{pp-semi-indef}}

{{Use dmy dates|date=October 2012}}
{{Redirect category shell|
{{About| the visual condition}}
{{R from alternative name}}
{{Infobox disease
{{R from merge}}
| Name = Blindness
{{R mentioned in hatnote}}
| ICD10 = {{ICD10|H|54|0|h|53}}, {{ICD10|H|54|1|h|53}}, {{ICD10|H|54|4|h|53}}
| ICD9 = {{ICD9|369}}
| MeSH=D001766
| Image = Long cane.jpg
| Caption = A [[white cane]], the international symbol of blindness
| Width = 100
| ICDO =
| OMIM =
| DiseasesDB = 28256
| MedlinePlus =
| eMedicineSubj =
| eMedicineTopic =
}}
}}
⚫
{{Authority control}}
'''Blindness''' is the condition of poor [[visual perception]].


Various scales have been developed to describe the extent of [[vision loss]] and define blindness.<ref name="ICO">International Council of Ophthalmology. [http://www.icoph.org/pdf/visualstandardsreport.pdf "International Standards: Visual Standards — Aspects and Ranges of Vision Loss with Emphasis on Population Surveys."] April 2002.</ref> Total blindness is the complete lack of form and visual light perception and is clinically recorded as NLP, an abbreviation for "no light perception."<ref name="ICO"/> Blindness is frequently used to describe severe [[visual impairment]] with some remaining vision. Those described as having only light perception have no more sight than the ability to tell light from dark and the general direction of a [[light source]]. The [[World Health Organization]] defines ''low vision'' as visual acuity of less than 20/60 (6/18), but equal to or better than 20/200 (6/60), or 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 20/400 (6/120), or a visual field loss to less than 10 degrees, in the better eye with best possible correction.<ref>http://www3.who.int/icd/currentversion/fr-icd.htm</ref><ref name=WHO2013>{{cite web| title = Visual impairment and blindness Fact Sheet N°282| publisher = [[World Health Organization]]| date=October 2013| url = http://www.who.int/mediacentre/factsheets/fs282/en/index.html| accessdate=4 May 2014}}</ref>

<!-- Epidemiology -->
As of 2012 there were 285 million visually impaired people in the world, of which 246 million had low vision and 39 million were blind.<ref name=WHO2013/> The majority of people with poor vision are in the [[developing world]] and are over the age of 50 years.<ref name=WHO2013/>

{{TOC limit|3}}
==Definition==<!--"Legally-blind" redirects to this section-->
Blindness is defined by the [[World Health Organization]] as vision in a person's best eye of less than 20/500 or a [[visual field]] of less than 10 degrees.<ref>{{cite journal|last=Maberley|first=DA|author2=Hollands, H|author3=Chuo, J|author4=Tam, G|author5=Konkal, J|author6=Roesch, M|author7=Veselinovic, A|author8=Witzigmann, M|author9=Bassett, K|title=The prevalence of low vision and blindness in Canada.|journal=Eye (London, England)|date=March 2006|volume=20|issue=3|pages=341–6|pmid=15905873|doi=10.1038/sj.eye.6701879}}</ref> This definition was set in 1972, and there is ongoing discussion as to whether it should be altered somewhat.<ref>http://www.who.int/blindness/Change%20the%20Definition%20of%20Blindness.pdf</ref>

Blind people with undamaged eyes may still register light non-visually for the purpose of [[Circadian rhythm|circadian]] [[Entrainment (chronobiology)|entrainment]] to the 24-hour light/dark cycle. Light signals for this purpose travel through the [[retinohypothalamic tract]] and are not affected by optic nerve damage beyond where the retinohypothalamic tract exits.

===United States===
In 1934, the [[American Medical Association]] adopted the following definition of blindness: <blockquote>
"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>
</blockquote>

The [[United States Congress]] included this definition as part of the Aid to the Blind program in the [[Social Security (United States)#Creation: The Social Security Act|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<ref>http://www.ssa.gov/history/pdf/80chap12.pdf</ref> which currently states: <blockquote>
"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 17 February 2006.</ref>
</blockquote>

===United Kingdom===
In the [[UK]], the Certificate of Vision Impairment (CVI) is used to certify patients as severely sight impaired or sight impaired.<ref>[http://www.dh.gov.uk/en/Healthcare/Primarycare/Optical/DH_4074843 "Identification and notification of sight loss"]</ref> The accompanying guidance for clinical staff states: "The National Assistance Act 1948 states that a person can be certified as severely sight impaired if they are “so blind as to be unable to perform any work for which eye sight is essential” (National Assistance Act Section 64(1)). The test is whether a person cannot do any work for which eyesight is essential, not just his or her normal job or one particular job."<ref name="dh.gov.uk">[http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/documents/digitalasset/dh_078294.pdf "Certificate of Vision Impairment: Explanatory Notes for Consultant Ophthalmologists and Hospital Eye Clinic Staff"]</ref>

In practice, the definition depends on individuals' [[visual acuity]] and the extent to which their [[field of vision]] is restricted. The [[Department of Health]] identifies three groups of people who may be classified as severely visually impaired.<ref name="dh.gov.uk"/>
#Those below 3/60 (equivalent to 20/400 in US notation) [[Snellen chart|Snellen]] (most people below 3/60 are severely sight impaired),
#Those better than 3/60 but below 6/60 Snellen (people who have a very contracted field of vision only),
#Those 6/60 Snellen or above (people in this group who have a contracted [[field of vision]] especially if the contraction is in the lower part of the field),

The Department of Health also state that a person is more likely to be classified as severely visually impaired if their eyesight has failed recently or if they are an older individual, both groups being perceived as less able to adapt to their vision loss.<ref name="dh.gov.uk"/>

===Other===
[[Kuwait]] is one of many nations that share the 6/60 criteria for legal blindness.<ref name="Al-Merjan">{{cite journal | last1 = Al-Merjan | first1 = JI | last2 = Pandova | first2 = MG |last3 = Al-Ghanim | first3 = M | last4 = Al-Wayel | first4 = A | last5 = Al-Mutairi | first5 = S |title = Registered blindness and low vision in Kuwait | journal = Ophthalmic epidemiology | volume = 12 | issue = 4 | pages = 251–7 | year = 2005 | pmid = 16033746 | doi = 10.1080/09286580591005813}}</ref>

==References==
{{Reflist|30em}}

==External links==
{{wikiquote|Blindness}}
*{{Wiktionary-inline|blindness|blind}}
<!--This section should only link to blindness web directories; Wpedia isn't a directory of blindness organisations etc.see Wikipedia:External links-->
*{{dmoz|Health/Conditions_and_Diseases/Eye_Disorders/Blindness|Blindness}}
*{{cite EB1911|wstitle=Blindness}}
{{Eye pathology}}

⚫
{{Authority control}}
[[Category:Blindness| ]]
[[Category:Blindness| ]]
[[Category:Visual disturbances and blindness]]
[[Category:Visual disturbances and blindness]]

Latest revision as of 11:24, 8 October 2023

Redirect to:

Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Blindness&oldid=1179174562"