The Snellen chart is commonly used to measure visual acuity at what distance?

The Snellen chart is commonly used to measure visual acuity at what distance?

• A. 20 feet
• B. 10 feet
• C. 30 feet
• D. 40 feet

Answer: (A)

Measuring visual acuity with the Snellen chart uses a fixed testing distance of 20 feet (about 6 meters). This standard distance lets the chart’s letter sizes correspond to consistent acuity levels. When someone reads at 20 feet the size of letters that a person with normal vision can read at 20 feet, that person is said to have 20/20 vision. If they can read at 20 feet only what a person with normal vision could read at 40 feet, their acuity is 20/40, indicating reduced sharpness. Some places use 6 meters in place of 20 feet, but the idea remains the same: a constant distance ensures meaningful, comparable measurements of how clearly a person sees at distance.

Measuring visual acuity with the Snellen chart uses a fixed testing distance of 20 feet (about 6 meters). This standard distance lets the chart’s letter sizes correspond to consistent acuity levels. When someone reads at 20 feet the size of letters that a person with normal vision can read at 20 feet, that person is said to have 20/20 vision. If they can read at 20 feet only what a person with normal vision could read at 40 feet, their acuity is 20/40, indicating reduced sharpness. Some places use 6 meters in place of 20 feet, but the idea remains the same: a constant distance ensures meaningful, comparable measurements of how clearly a person sees at distance.