A person with 20/20 vision can see what a typical person can see when they are 20 feet away, according to How Stuff Works. Being able to see at 20 feet what the average person can see at 13 feet makes someone with 20/13 vision above average.
How Stuff Works claims that 20/20 vision is typical for humans. However, a person’s eyesight gets worse the higher the second number in this percentage rises. A person is deemed legally blind, for instance, if their measured eyesight is 20/200.
The strength of that person’s vision, however, increases as the second number decreases. 20/10 vision is considered to be really good eyesight.