Snellen chart

A Snellen chart is a tool used to measure visual acuity, which is how well someone can see. It consists of rows of letters that gradually decrease in size. During an eye exam, a person stands a specific distance away, typically 20 feet, and reads the letters aloud, starting from the largest. The smallest letters they can read indicate their vision level. For example, if someone reads to the smallest line marked "20/20," it means they have normal vision. Lower numbers indicate poorer vision, while higher numbers (like 20/40) suggest less clarity at that distance.