20/20 vision a term used to describe normal visual acuity -- the sharpness of a person's vision -- measured at a distance of 20 feet. If a person has 20/20 vision it means that they can see clearly at 20 feet what should normally be seen at a distance. If someone has 20/100 vision it means that they must be as close to 20 feet as possible to see what a person with normal vision could see at 100 feet.

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