Blindness refers to severely diminished vision, but the specific criteria used to categorize someone as being blind vary depending on location and context. One might think of a blind person as having absolutely no visual sensitivity and living in total darkness. Yet most individuals with blindness can at least perceive light, and some have enough pattern vision to count fingers.

The definition of blindness in the United States is someone who has an acuity in the better eye of 20/200 or worse (meaning a pattern that is recognizable at a distance of 200 feet for a person with normal vision can only be recognized at a distance of 20 feet) or has a visual field of view of 20 degrees or less (a person with normal ...

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