Vision standard: In the USA the standard is the Snellen fraction of 20/20. The upper number means the letters are 20 feet away. The lower is the distance the normal could be to read the number. If someone is 20/200 at best, the letter is large enough that the 20/20 normal could be 200 feet away and still read it. Visual charts have a graded series of letter size to get the best fit.
Answered 7/9/2014
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A doctor has provided 1 answer
A doctor has provided 1 answer
A doctor has provided 1 answer
A doctor has provided 1 answer
A doctor has provided 1 answer
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