Related topics: eye , retina , vision loss
Blindness
hideBlindness 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. Total blindness is the complete lack of form and visual light perception and is clinically recorded as NLP, an abbreviation for "no light perception." Blindness is frequently used to describe severe visual impairment with residual 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.
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. 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 (6.1 m) from an object to see it—with vision correction—with the same degree of clarity as a normally sighted person could from 200 feet (61 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.
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 (20/60), but equal to or better than 3/60 (20/400), 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 (20/400), or corresponding visual field loss to less than 10 degrees, in the better eye with best possible correction.
It should be noted that blind people with undamaged eyes may still register light non-visually for the purpose of circadian entrainment to the 24-hour light/dark cycle. Light signals for this purpose travel through the retinohypothalamic tract, so a damaged optic nerve beyond where the retinohypothalamic tract exits it is no hindrance.
For more information about Blindness, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with blindness
The changing pattern of childhood blindness in developing countries
Dec 08, 2009 |
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"Changing patterns of global childhood blindness suggest a reassessment of research, training, and programmatic needs," says a team of eye specialists from India, Malawi, and Tanzania.
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Science's breakthrough of the year: Uncovering 'Ardi'
Dec 17, 2009 |
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The research that brought to light the fossils of Ardipithecus ramidus, a hominid species that lived 4.4 million years ago in what is now Ethiopia, has topped Science's list of this year's most significant s ...
Device connected to tongue designed to help blind perceive images
Dec 15, 2009 |
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An experimental device that uses the tongue instead of the eyes to "see" could be on the market next year, and a blind Fresno, Calif., teen hopes to be among the first to take one home.
Discovery of new gene called Brd2 that regulates obesity and diabetes
Dec 15, 2009 |
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The chance discovery of a genetic mutation that makes mice enormously fat but protects them from diabetes has given researchers at Boston University School of Medicine, USA, new insights into the cellular mechanisms that ...
Efforts under way to make Web more accessible
Electronics / Consumer & Gadgets
Dec 15, 2009 |
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(AP) -- Imagine not being able to use a mouse to open a Web browser or a keyboard to type an e-mail. What if you couldn't distinguish colors on a computer screen or type the distorted letters in order to ...
Steroid injections may slow diabetes-related eye disease
Dec 15, 2009 |
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Injecting the corticosteroid triamcinolone into the eye may slow the progression of diabetic retinopathy, a complication of diabetes that can cause vision loss and blindness, according to a report in the December issue of ...
Study shows how gene action may lead to diabetes prevention, cure
Dec 11, 2009 |
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A gene commonly studied by cancer researchers has been linked to the metabolic inflammation that leads to diabetes.
Successful stem cell therapy for treatment of eye disease
Dec 10, 2009 |
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Newly published research, by investigators, at the North East England Stem Cell Institute (NESCI) in the journal Stem Cells reported the first successful treatment of eight patients with "Limbal Stem Cell Deficiency" (LSCD) ...
Umbilical stem cells may help recover lost vision for those with corneal disease
Dec 08, 2009 |
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(PhysOrg.com) -- New research from the University of Cincinnati (UC) may help in the recovery of lost vision for patients with corneal scarring.
Mice holding back muscular dystrophy research
Dec 04, 2009 |
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Humans and mice have previously unknown and potentially critical differences in one of the genes responsible for Duchenne muscular dystrophy (DMD). Researchers writing in the open access journal BMC Biology have found that t ...
Scientists rescue visual function in rats using induced pluripotent stem cells
Dec 03, 2009 |
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An international team of scientists has rescued visual function in laboratory rats with eye disease by using cells similar to stem cells. The research shows the potential for stem cell-based therapies to treat ...
List of search results for blindness
