What is a common test used to measure visual acuity?

The Snellen chart is the standard tool used to measure visual acuity. This test typically displays letters of varying sizes on a chart, and patients are asked to read the smallest letters they can see clearly from a specific distance, usually 20 feet. The results are recorded as a fraction, where the top number represents the distance at which the test is performed and the bottom number indicates the distance at which a person with normal vision would be able to read the letters.

This method is widely recognized and is a fundamental assessment in both clinical and school settings for determining a person's visual clarity. It provides a clear metric for eye care professionals to evaluate the sharpness of vision and monitor changes over time, making it an essential component of eye examinations.

In contrast, the Amsler grid is specifically used for detecting macular degeneration and other central vision issues, the Ishihara test is designed for assessing color vision deficiencies, and the contrast sensitivity test evaluates the ability to perceive differences in visual contrast rather than clear acuity. Each of these tests serves distinct purposes and does not directly measure overall visual acuity like the Snellen chart.