What is 20/20 Vision?

20/20 describes distance visual acuity on a standardized chart. It is a useful measure of detail vision, but it does not mean every part of your vision or eye health is perfect.

Understanding the numbers

The first number is the testing distance in feet. The second indicates the distance at which the reference observer could resolve the same line. With 20/40 acuity, a person at 20 feet resolves detail that the reference observer could resolve at 40 feet. See the NEI visual-acuity definition.

At a fixed test distance, the letters on the 20/40 line are twice the size of those on the 20/20 line. A lower second number, such as 20/15, represents finer measured detail vision under those test conditions. A 6/6 result uses meters and expresses the same ratio as 20/20.

What the chart does not tell us

Chart acuity alone does not describe peripheral vision, contrast sensitivity, eye coordination, color vision, or the health of the retina and optic nerve. Whether acuity was measured with or without glasses also matters. A comprehensive eye examination puts the result in context.