To be considered legally blind in the United States, a person must meet specific criteria regarding visual acuity and visual field. According to the Social Security Act, an individual is considered legally blind if their best-corrected visual acuity for distance in the better eye is 20/200 or less, or if their visual field is 20 degrees or less in the better-seeing eye. This means that even with the use of glasses or contact lenses, they can only read the top letter on the Snellen Chart, or they have a severely constricted visual field. Its important to note that being legally blind does not necessarily mean total blindness, as legally blind individuals may still have some level of vision, albeit significantly impaired.

The federal definition of legal blindness is used to determine eligibility for various benefits, vocational training, rehabilitation, schooling, low vision devices, and tax exemption programs. It is also important to consult a doctor for an accurate diagnosis of legal blindness, as it has implications for driving and eligibility for certain benefits and programs.

In summary, legal blindness is determined by specific visual acuity and visual field criteria, and it is distinct from total blindness. It is a legal designation used for eligibility for various benefits and programs, and individuals should seek professional medical evaluation to determine their status.