When you visit the eye doctor for a checkup, you may be asked to read an eye chart. The chart measures your visual acuity, or sharpness of vision. If you don’t wear glasses or contacts, your eye doctor will use the results to find out whether you need them. If you wear corrective lenses, the results will show if your prescription needs to change.

The eye chart is used to measure visual acuity, which refers to how well you can see without glasses or contacts. The results are used to determine if you need eyewear to correct your vision. It's part of a general assessment of your overall eye health. This article explains how the eye chart works and what some benchmark results may mean.