Question:

What does it mean to be legally blind?

Answer:

“Legally blind” is an administrative term used by agencies and organizations that provide compensation and/or rehabilitation to patients with permanent vision loss. The term is not very useful clinically, because optometrists always begin their examinations with measurement of visual acuity and then try to improve the quantity and quality of the initial measurement.

To satisfy the definition of “legally blind”, patients must have permanent vision loss of 20/200 (i.e., the patient sees at 20 feet what normals see at 200 feet) or less best corrected visual acuity in the better eye, or have a visual field of less than 20 degrees (NOTE: you can simulate this by overlapping your index finger with your thumb, and then looking through the “hole”). There are several critical elements in this definition:

1. The vision loss must be permanent; so if you have an advanced cataract which causes poor vision, but then have a cataract operation to restore your sight, you were never really “legally blind”.

2. All measurements are made with the best glasses prescription in place; so if your vision is blurred without glasses but better than 20/200 with glasses, you are not legally blind.

3. The patient’s better eye is the most important one when determining legal blindness; if you have no vision at all in one eye, but better than 20/200 with glasses in the other, you are not legally blind.

4. Finally, there are some eye diseases that affect side vision more than central vision; and it is possible to have perfect central vision but severely reduced side vision and then be classified as legally blind.

Not all patients who are legally blind need to read Braille, have a pilot dog, or walk with a white cane – these extreme rehabilitative techniques are reserved for patients who cannot see a hand wave in front of their eyes. Most legally blind patients have some remaining sight, but it is not enough to perform daily activities like driving and reading a newspaper.

Optometrists who specialize in vision rehabilitation are called low vision experts; and they have many types of optical and electronic aids that can help a legally blind patient adapt to his or her permanent loss of sight.

For more information:

Go to the Eye and Vision Care health topic.