Adapted from the National Eye Institute, U.S. National Institutes of Health. Available online: http://www.nei.nih.gov

An E chart is used to test the far vision of children and people who cannot read. It has several rows, which contain only the letter E in different positions. The top row is the largest and the bottom row of Es is the smallest. You stand 20 ft (6 m) from the chart, cover one eye, and indicate the smallest row you can see on the chart by pointing in the same direction as the lines of the E.

Similar charts use the letter C or pictures.