How far should a person stand to conduct a Snellen test?

The Snellen test is specifically designed to assess visual acuity, and standard practice dictates that the individual undergoing the test should stand exactly 20 feet away from the chart. This distance allows for the most accurate measurement of visual acuity. The chart itself is calibrated to reflect this distance, ensuring that the letters on the chart are of a specific size appropriate for testing.

When conducting a Snellen test, standing at the correct distance is crucial to assess how well a person can see at a distance compared to what is considered normal vision. It is important to adhere to this standard distance for consistency and reliability in the results.

While other distances proposed may seem reasonable, they will compromise the reliability of the results. For example, standing closer or further than the established distance can lead to incorrect assessments of visual acuity. Therefore, 20 feet is the distance recommended for conducting a Snellen test.