In order to be considered legally blind, someone must have vision of 20/200 (6/60) in his or her best eye with correction, and/or have a visual field which is limited to 20 degrees or less, in contrast with the 180 degree visual field enjoyed by people with healthy eyes. This definition means that it is possible for someone to be able to see and to still be considered blind in the eyes of the law.
Governments have come up with a definition for legal blindness for the purpose of being able to determine who should receive special government benefits and assistance for blindness. Someone who is legally blind may be entitled to disability payments and other assistance, such as note takers in college classes, or aids such as seeing eye dogs, canes, and so forth which will help them navigate the world.
Source:http://www.wisegeek.com/what-does-legally-blind-mean.htm
