Visual impairment

Visual impairment

Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment– visual impairment may cause the individual difficulties with normal daily tasks including reading and walking.<a href="#cite_note-6" style="counter-reset: mw-Ref 6;">[6]</a> Low vision is a functional definition of visual impairment that is chronic, uncorrectable with treatment or correctable lenses, and impacts daily living. As such low vision can be used as a disability metric and varies based on an individual's experience, environmental demands, accommodations, and access to services. The American Academy of Ophthalmology defines visual impairment as the best-corrected visual acuity of less than 20/40 in the better eye,<a href="#cite_note-7" style="counter-reset: mw-Ref 7;">[7]</a> and the World Health Organization defines it as a presenting acuity of less than 6/12 in the better eye.<a href="#cite_note-8" style="counter-reset: mw-Ref 8;">[8]</a> The term blindness is used for complete or nearly complete vision loss. In addition to the various permanent conditions, fleeting temporary vision impairment, <a href="/en/Amaurosis_fugax" title="Amaurosis fugax" class="wl">amaurosis fugax</a>, may occur, and may indicate serious medical problems. The abbreviation VIP is sometimes used for Visually Impaired Person, Persons or People.<a href="#cite_note-9" style="counter-reset: mw-Ref 9;">[9]</a><a href="#cite_note-10" style="counter-reset: mw-Ref 10;">[10]</a><a href="#cite_note-11" style="counter-reset: mw-Ref 11;">[11]</a>


<div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none" about="#mwt1">Decreased ability to see</div>
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<div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none" about="#mwt13">Medical condition</div><style data-mw-deduplicate="TemplateStyles:r1066479718" typeof="mw:Extension/templatestyles">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}body.skin-minerva .mw-parser-output .infobox-header,body.skin-minerva .mw-parser-output .infobox-subheader,body.skin-minerva .mw-parser-output .infobox-above,body.skin-minerva .mw-parser-output .infobox-title,body.skin-minerva .mw-parser-output .infobox-image,body.skin-minerva .mw-parser-output .infobox-full-data,body.skin-minerva .mw-parser-output .infobox-below{text-align:center}</style><div class='mobile-collapse'><header class="mobile-collapse-header mobile-collapse-btn">Quick facts: Visual impairment, Other names, Specialty, Sy... ▼</header> <table class="infobox mobile-collapse-element"><tbody><tr><th colspan="2" class="infobox-above notheme" style="background:#ccc">Visual impairment</th></tr><tr><th scope="row" class="infobox-label">Other names</th><td class="infobox-data">Vision impairment, vision loss</td></tr><tr><td colspan="2" class="infobox-full-data"><a href="/en/File:Long_cane.jpg" class="mw-file-description image media-thumb" data-hash="File:Long_cane.jpg"><img loading="lazy"alt="Long cane, white with a red band" src="//upload.wikimedia.org/wikipedia/commons/thumb/c/ce/Long_cane.jpg/120px-Long_cane.jpg" decoding="async" data-file-width="521" data-file-height="2262" data-file-type="bitmap" height="521" width="120" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/ce/Long_cane.jpg/180px-Long_cane.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/ce/Long_cane.jpg/240px-Long_cane.jpg 2x"></a></td></tr><tr><td colspan="2" class="infobox-full-data">A <a href="/en/White_cane" title="White cane" class="wl">white cane</a>, the international symbol of blindness</td></tr><tr><th scope="row" class="infobox-label"><a href="/en/Medical_specialty" title="Medical specialty" class="wl">Specialty</a></th><td class="infobox-data"><a href="/en/Ophthalmology" title="Ophthalmology" class="wl">Ophthalmology</a></td></tr><tr><th scope="row" class="infobox-label"><a href="/en/Signs_and_symptoms" title="Signs and symptoms" class="wl">Symptoms</a></th><td class="infobox-data">Decreased ability to <a href="/en/Visual_perception" title="Visual perception" class="wl">see</a><a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a><a href="#cite_note-CDC2011-2" style="counter-reset: mw-Ref 2;">[2]</a></td></tr><tr><th scope="row" class="infobox-label"><a href="/en/Complication_(medicine)" title="Complication (medicine)" class="wl">Complications</a></th><td class="infobox-data"><a href="/en/Non-24-hour_sleep–wake_disorder" title="Non-24-hour sleep–wake disorder" class="wl">Non-24-hour sleep–wake disorder</a>, <a href="/en/Falls_in_older_adults" title="Falls in older adults" class="wl">falls in older adults</a><a href="#cite_note-3" style="counter-reset: mw-Ref 3;">[3]</a><a href="#cite_note-4" style="counter-reset: mw-Ref 4;">[4]</a></td></tr><tr><th scope="row" class="infobox-label">Causes</th><td class="infobox-data">Uncorrected <a href="/en/Refractive_errors" title="Refractive errors" class="mw-redirect wl">refractive errors</a>, <a href="/en/Cataract" title="Cataract" class="wl">cataracts</a>, <a href="/en/Glaucoma" title="Glaucoma" class="wl">glaucoma</a><a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a></td></tr><tr><th scope="row" class="infobox-label"><a href="/en/Medical_diagnosis" title="Medical diagnosis" class="wl">Diagnostic method</a></th><td class="infobox-data"><a href="/en/Eye_examination" title="Eye examination" class="wl">Eye examination</a><a href="#cite_note-CDC2011-2" style="counter-reset: mw-Ref 2;">[2]</a></td></tr><tr><th scope="row" class="infobox-label">Treatment</th><td class="infobox-data"><a href="/en/Vision_rehabilitation" title="Vision rehabilitation" class="wl">Vision rehabilitation</a>, changes in the environment, assistive devices (<a href="/en/Eyeglasses" title="Eyeglasses" class="mw-redirect wl">eyeglasses</a>, <a href="/en/White_cane" title="White cane" class="wl">white cane</a>)<a href="#cite_note-CDC2011-2" style="counter-reset: mw-Ref 2;">[2]</a></td></tr><tr><th scope="row" class="infobox-label">Frequency</th><td class="infobox-data">940 million / 13% (2015)<a href="#cite_note-GBD2015Pre-5" style="counter-reset: mw-Ref 5;">[5]</a></td></tr></tbody></table> <footer class='mobile-collapse-footer mobile-collapse-btn'>Close ▲</footer></div>

The most common causes of visual impairment globally are uncorrected <a href="/en/Refractive_errors" title="Refractive errors" class="mw-redirect wl">refractive errors</a> (43%), <a href="/en/Cataract" title="Cataract" class="wl">cataracts</a> (33%), and <a href="/en/Glaucoma" title="Glaucoma" class="wl">glaucoma</a> (2%).<a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a> Refractive errors include <a href="/en/Near-sightedness" title="Near-sightedness" class="wl">near-sightedness</a>, <a href="/en/Far-sightedness" title="Far-sightedness" class="wl">far-sightedness</a>, <a href="/en/Presbyopia" title="Presbyopia" class="wl">presbyopia</a>, and <a href="/en/Astigmatism_(eye)" title="Astigmatism (eye)" class="mw-redirect wl">astigmatism</a>.<a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a> Cataracts are the most common cause of blindness.<a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a> Other disorders that may cause visual problems include <a href="/en/Age-related_macular_degeneration" title="Age-related macular degeneration" class="mw-redirect wl">age-related macular degeneration</a>, <a href="/en/Diabetic_retinopathy" title="Diabetic retinopathy" class="wl">diabetic retinopathy</a>, <a href="/en/Corneal_opacification" title="Corneal opacification" class="mw-redirect wl">corneal clouding</a>, <a href="/en/Childhood_blindness" title="Childhood blindness" class="wl">childhood blindness</a>, and a number of <a href="/en/Infection" title="Infection" class="wl">infections</a>.<a href="#cite_note-WHO2012Data-12" style="counter-reset: mw-Ref 12;">[12]</a> Visual impairment can also be caused by problems in the <a href="/en/Brain" title="Brain" class="wl">brain</a> due to <a href="/en/Stroke" title="Stroke" class="wl">stroke</a>, <a href="/en/Premature_birth" title="Premature birth" class="mw-redirect wl">premature birth</a>, or trauma, among others.<a href="#cite_note-Leh2012-13" style="counter-reset: mw-Ref 13;">[13]</a> These cases are known as <a href="/en/Cortical_visual_impairment" title="Cortical visual impairment" class="wl">cortical visual impairment</a>.<a href="#cite_note-Leh2012-13" style="counter-reset: mw-Ref 13;">[13]</a> Screening for vision problems in children may improve future vision and educational achievement.<a href="#cite_note-14" style="counter-reset: mw-Ref 14;">[14]</a> Screening adults without symptoms is of uncertain benefit.<a href="#cite_note-USPSTF2016-15" style="counter-reset: mw-Ref 15;">[15]</a> Diagnosis is by an <a href="/en/Eye_exam" title="Eye exam" class="mw-redirect wl">eye exam</a>.<a href="#cite_note-CDC2011-2" style="counter-reset: mw-Ref 2;">[2]</a>


The <a href="/en/World_Health_Organization" title="World Health Organization" class="wl">World Health Organization</a> (WHO) estimates that 80% of visual impairment is either preventable or curable with treatment.<a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a> This includes cataracts, the infections <a href="/en/Onchocerciasis" title="Onchocerciasis" class="wl">river blindness</a> and <a href="/en/Trachoma" title="Trachoma" class="wl">trachoma</a>, glaucoma, diabetic retinopathy, uncorrected refractive errors, and some cases of childhood blindness.<a href="#cite_note-WHO2015Cause-16" style="counter-reset: mw-Ref 16;">[16]</a> Many people with significant visual impairment benefit from <a href="/en/Vision_rehabilitation" title="Vision rehabilitation" class="wl">vision rehabilitation</a>, changes in their environment, and assistive devices.<a href="#cite_note-CDC2011-2" style="counter-reset: mw-Ref 2;">[2]</a>


As of 2015<a rel="mw:ExtLink" href="//en.wikipedia.org/w/index.php?title=Visual_impairment&amp;action=edit" class="external text" target="_blank">[update]</a>, there were 940 million people with some degree of vision loss.<a href="#cite_note-GBD2015Pre-5" style="counter-reset: mw-Ref 5;">[5]</a> 246 million had low vision and 39 million were blind.<a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a> The majority of people with poor vision are in the <a href="/en/Developing_world" title="Developing world" class="mw-redirect wl">developing world</a> and are over the age of 50 years.<a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a> Rates of visual impairment have decreased since the 1990s.<a href="#cite_note-WHO2014-1" style="counter-reset: mw-Ref 1;">[1]</a> Visual impairments have considerable economic costs both directly due to the cost of treatment and indirectly due to decreased ability to work.<a href="#cite_note-17" style="counter-reset: mw-Ref 17;">[17]</a>
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Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment– visual impairment may cause the individual difficulties with normal daily tasks including reading and walking. The most common causes of visual impairment globally are uncorrected refractive errors , cataracts , and glaucoma . The World Health Organization estimates that 80% of visual impairment is either preventable or curable with treatment. 