Description
This article is from the Vision and Eye
Care FAQ, by grants@research.canon.com.au (Grant Sayer) with
numerous contributions by others.
1.6 How is Visual Acuity Measured
Visual acuity is the measure of the sensitivity of the visual system.
It is expressed in Snellen notation, expressed as a fraction, where the
numerator indicates the test distance and the denominator denotes the
distance at which the letter read by the patient subtends 5 minutes of arc.
Normal vision is expressed as 20/20 (or 6/6 in countries where metric
measurements are used).
An acuity of 20/60 means that the patient was tested at 20feet but could
only see letters that a person with normal vision could read at 60feet.
Other WWW references:
URL: http://www.west.net/~eyecare/visual_acuity.html
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