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What does it mean to be legally blind?

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Updated April 05, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Question: What does it mean to be legally blind?
Answer: A person is considered to be legally blind if he or she has a best corrected vision of 20/200 in their best seeing eye.

Many people feel that they are legally blind because when they remove their glasses or contact lenses, they cannot see a foot in front of their face. However, when they put on their vision correction, they can see 20/20. As long as you can be corrected to 20/20 with some visual aid, you are not considered legally blind.

The true definition of "legal blindness" is based upon the best level of vision that you can achieve or the best vision you can be corrected to. Most government agencies and health care institutions agree that legal blindness is defined as one of the following:

  1. Legal blindness is defined as visual acuity of 20/200 or worse in the best seeing eye.
  2. A visual field that is limited to only 20 degrees.

What does "legally blind" really mean?

Being legally blind means that your best seeing eye cannot be corrected with glasses or contact lenses any better than 20/200. The best way to understand this is to think about a normal person with 20/20 vision. This person has the ability to stand 200 feet away from an object and see the finest detail, whereas the legally blind person would have to move all of the way up to 20 feet to see the same detail. A legally blind person has difficulty seeing objects very far away or very close.

If a person has a visual field of only 20 degrees, considered tunnel vision, he or she can be considered legally blind. A normal person has a visual field of 180 degrees. People with a limited visual field can see central detail but can't see someone standing right next to their own shoulder. These people have difficulty with mobility, as safe driving is nearly impossible. Walking into a dark movie theater can also be a major problem.

The definition of legal blindness was developed to help people receive government assistance. Also, as you can imagine, the department of motor vehicles (DMV) has to have some way of measuring vision in order to keep our roads and highways safe.

Source:

Lavine, Jay B. The Eye Care Sourcebook, pp 24-25. Contemporary Books, 2001.

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