Approximately 500,000 Americans have vision impairments to the extent that they are considered "legally blind." There are three degrees of vision loss:
Visual Acuity of 20/200
The legally blind person can see at 20 feet what the average-sighted person can see at 200.
Limited or diminished vision that cannot be corrected with standard lenses.
The field of vision is impaired because of an illness, a degenerative syndrome, or trauma. Only two percent of the people with vision impairments are totally blind; most blind people have some amount of usable vision.