Ophthalmology

First 3D-printed human corneas

The first human corneas have been 3-D printed by scientists at Newcastle University, UK.

Immunology

New insights into why the immune system fails to see cancer

Cancer hides in plain sight of the immune system. The body's natural tumor surveillance programs should be able to detect and attack rogue cancer cells when they arise, and yet when cancer thrives, it does so because these ...

Ophthalmology

Eye surgeon uses stem cells to repair damaged corneas

In Hyderabad, India, Sayan Basu is using stem cells in a pilot project to restore the eyesight of patients with damaged corneas. If proven successful, the procedure could mean that Indian citizens can avoid long waiting lists ...

Neuroscience

Resveratrol impacts Alzheimer's disease biomarker

The largest nationwide clinical trial to study high-dose resveratrol long-term in people with mild to moderate Alzheimer's disease found that a biomarker that declines when the disease progresses was stabilized in people ...

Medical research

A possible cure for river blindness and elephantiasis

An international team of researchers has found what might be a cure for river blindness and elephantiasis. In their paper published in the journal Science Translational Medicine, the group describes their search for a drug ...

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 ...

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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