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What Is Legal Blindness And What Tests Help Diagnose It?

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If you are severely nearsighted, even with your glasses on, you could qualify as being legally blind. However, you must have an eye examination with specific tests to determine if you have the condition. Legal blindness is often not what most people think. Here is more information about legal blindness and how the optometrist tests for the condition.

What Is Legal Blindness?

In the United States, the basic definition of legal blindness is if your best-corrected vision is less than 20/200 in your best eye. The 20/200 refers to the basic Snellen eye chart. This chart is standard use for any eye examination. The Snellen test measures what a person with normal vision should see at certain distances. In this case, if you were 20/200, then you would have to be 20 feet or less to see what someone else can see from 200 feet.

Another criterion for legal blindness is if your field of vision is 20 degrees or less. The normal field of vision for human beings varies but is generally around 180-190 degrees for both eyes together. Even if you have perfect vision, a 20-degree visual field is highly restrictive. You mostly only see what is directly in front of you unless you turn your head.

What Is NOT Legal Blindness?

Even if you are legally blind in one eye, you are not legally blind if the other eye has better than 20/200 vision on an eye examination. Legal blindness refers to your best-corrected vision, not your vision without glasses. Your natural eyesight might be worse than 20/200 vision but normal with correction. Legal blindness also isn't the inability to correct to normal vision. You can still see poorly with corrective lenses but not be considered legally blind.

What Tests Help Determine Legal Blindness?

In addition to traditional eye tests, your optometrist may also include a more extensive examination of your visual field. You may also receive more in-depth retinal examinations. The tests may also check for certain neurological responses and other internal issues. The doctor may also test for other diseases and issues that could contribute to your blindness, like glaucoma. Tests may be especially extensive if you plan to apply for disability benefits.

If you need an official diagnosis of legal blindness, then talk to your optometrist. You may need to take more than the standard eye examination tests to confirm your condition. Even if you are diagnosed as legally blind, your condition could improve. Regular eye examinations are important, especially if you have low vision. If you have questions about eye exams, contact a local eye care clinic.