Legally Blind
In the United States, Legal Blindness is defined as a visual acuity lower than or equal to 20/200 in the better eye, with best correction -or- a visual field of less than 20 degrees in diameter.
With 20/200 visual acuity, a person can see at 20 feet what a person with 20/20 vision sees at 200 feet.
Visual acuity is the ability to see fine details. Visual field refers to the part of a person’s vision that enables them to see what is happening to the side of them.