Tactile books adapted for blind children

Children's books play a key role in child development and access to culture. Books with tactile illustrations are particularly useful for understanding history. Yet it is essential that the illustrations are understood by ...

Diseases, Conditions, Syndromes

Study highlights 'moralisation' of COVID response and restrictions

A collaborative study led by the University of Otago has shown that COVID-19 containment and elimination efforts have become moralised. As a result, people are more likely to accept collateral damage from these efforts, such ...


Restoring a rudimentary form of vision in the blind

Restoration of vision in blind people through a brain implant is on the verge of becoming reality. Recent discoveries at the Netherlands Institute for Neuroscience (NIN) show that newly developed high-resolution implants ...

Oncology & Cancer

New drug for metastatic colorectal cancer enters phase 3 trial

A new therapy for metastatic colorectal cancer that has been granted fast-track designation by the U.S. Food and Drug Administration is being tested in a phase 3 clinical trial at Vanderbilt-Ingram Cancer Center.


Adding omega-3 fatty acids does not cut high CV risk

(HealthDay)—A carboxylic acid formulation of eicosapentaenoic acid and docosahexaenoic acid (omega-3 CA) does not improve outcomes among statin-treated patients at high cardiovascular risk, according to a study published ...

Psychology & Psychiatry

Missing the radiological forest for the trees

There's a classic video demonstrating how our brains process information and allocate attention in which people bounce and pass basketballs and the viewer is asked to count the passes.

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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. 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.

This text uses material from Wikipedia, licensed under CC BY-SA