A 39-year-old member asked:
what is the distance to measure nearsightedness at, and why?
1 doctor answer
Dr. Richard Bensinger answered
52 years experience Ophthalmology
20 feet: All lanes are corrected for distance to be equivalent to 20 feet which is the defined standard. In metric countries it is 6 meters. The snellen fraction 20/ over something, uses the 20 foot standard as part of the fraction. It is arbitrary but since a universal standard was needed for the optical industry, in the usa 20 feet is adopted for all to measure by.
Answered on Apr 25, 2013
People also searched for:
Connect by text or video with a U.S. board-certified doctor now — wait time is less than 1 minute!
$15 per month