Neuroscience

Can being born blind protect people from schizophrenia?

A study carried out by The University of Western Australia has provided compelling evidence that congenital/early cortical blindness – that is when people are blind from birth or shortly after—is protective against schizophrenia.

Autism spectrum disorders

Medical cannabis relieves symptoms in children with autism: study

In a new study of patients with autism who are 18 years old and under, researchers from Ben-Gurion University of the Negev (BGU) and Soroka University Medical Center report that cannabis as a treatment for autism spectrum ...

Neuroscience

How your moving brain sees the world

What we see is not only determined by what is really there, but also depends on whether we are paying attention, whether we are moving, excited or interested. In a new study published in Nature Communications, scientists ...

Neuroscience

Can the blind really hear better?

The human brain is extremely plastic, especially the visual processing centre. The function of the newly organised brain area in blindness is still a topic of intense debate.

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Blindness

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