Dr. Jim Martin 06/23/2015

Eye_Doctor_-_Vision_-_Tools-1.jpgBlindness is usually defined as complete loss of vision. However, someone can suffer with extreme loss of vision without becoming completely blind. At what point does loss of vision meet the standards of legal blindness?

There are two criteria used to determine if someone is legally blind: visual acuity and/or visual field restriction.

Visual Acuity

Visual acuity measures the clarity or acuteness of vision. 20/20 is usually used to define normal acuity. This indicates a person standing 20 feet from a vision chart can discern contours that are about 1.75 mm apart.

Someone who has a visual acuity of 20/200 or worse, with best correction, is considered legally blind. The 20/200 figure means that the affected person standing 20 feet in front of the eye chart can see what a normal 20/20 person can see at 200 feet. If you look at a typical eye chart, the large letter at the top (usually an "E") is 20/400. Best correction means the person is wearing prescription eyeglasses or contact lenses.

In 2007, the Social Security Administration updated its definition of legal blindness. If someone is tested using a low vision test chart, and cannot read any of the 20/100 lines, with best correction, that person qualifies as legally blind.

Visual Field Restrictions

In a person with normal vision, the horizontal range of vision is up to 60 degrees towards the nose and up to 100 degrees to the temple, measured from the vertical median of the eye. The vertical range of vision is 60 degrees above and 75 degrees below the horizontal median.

A person who only has 20 degrees of visual field is considered legally blind. This kind of vision is often called tunnel vision. The person can only see a small portal looking forward.

Why Is The Legal Definition Of Blindness So Important?

Being legally blind has several implications. It prevents people from obtaining driver's licenses and other permits where visual acuity is a requirement.

On the other hand, it opens up opportunities that are not available to those who are not legally blind. Some of those opportunities include treatment, aids, and training. There are some government and private contracts only available to those who are legally blind. Those who are legally blind may also qualify for disability payments from the federal government.

If you or a loved one is struggling with poor vision, you may meet the legal blindness criteria. This diagnosis must be made by a qualified eye doctor. Contact Broome Optical in Amarillo. We can test your eyes and let you know if you meet the legal criteria.

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