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What is the best method to measure visual acuity?
In the U.S., most eye doctors will use a Snellen eye chart, which provides an image of various sized letters and numbers at 20 feet. In some instances, an exam room may have mirrors with reflections of the eye chart on the wall to create an image at 20 feet. The "ETDRS" chart is another vision chart that is often used for ophthalmic studies as it is easy to convert the letters on this chart for statistical values to help better understand published results. Outside of the U.S., eye doctors may use a logMAR visual scale or a similar scale to the Snellen visual chart in which they measure vision in meters rather than feet. For children who do not know letters or numbers, a similar chart that provides images of well-known pictures at various sizes is referred to as an Allen chart. For babies, other tests are needed to assess visual function.
Answered by: W. Barry Lee, MD
Categories: General Eye Health
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Answered: Oct 22, 2013
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