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Article: Clearing up the mystery of 20/20 vision.
- Article from:
- The Boston Herald
- Article date:
- August 18, 1999
- Author:
CopyrightCOPYRIGHT 1999 Boston Herald. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Q: Overheard recently on the Martha Vineyard ferry) Her: What is the 20 in 20/20 vision? Him: It's, uh, the size of the numbers on the eye chart. Her: Yeah, right. More like your IQ. Him: At least we know it's not your age.
A: In 1862, Dutch optometrist Joseph Snellen set the noble goal of standardizing the science of vision testing. He devised what is today the most widely used eye chart (known as - surprise! - the Snellen Chart), and established benchmarks for "normal" vision.
According to Snellen's system, in the expression 20/20 vision, the first number indicates the distance at which a patient was able to read a particular line of the eye chart. ...