In the United States, a person is legally blind if his or her best eye has less than 20/200 vision with the help of glasses or contact lenses. Having 20/200 vision means that a person cannot be more than 20 ft (6.1 m) away to see what a person with normal vision can see from 200 ft (60.96 m) away.
Legal blindness does not mean that a person cannot see at all. People who are legally blind often have some vision, but their field of vision may be very narrow or blurry. Or they may have blind spots that glasses cannot correct.
Being diagnosed as legally blind restricts a person's ability to obtain a driver's license. But a legally blind person is usually eligible for low visibility aids and other benefits to help improve daily functioning.
WebMD Medical Reference from Healthwise