Which distance is used for near visual acuity testing?

Which distance is used for near visual acuity testing?

• A. 60 cm
• B. 20 cm
• C. 40 cm
• D. 100 cm

Answer: (C)

Near visual acuity testing uses a standard distance that reflects typical reading tasks. Forty centimeters is chosen because it matches how people usually hold reading material and keeps the accommodative demand around 2.5 diopters, allowing reliable, comparable measurements. Testing much closer, like twenty centimeters, would require about 5 diopters of accommodation and can distort results by stressing focusing ability. Distances such as sixty or one hundred centimeters assess distance or intermediate vision, not near tasks. So forty centimeters is the standard for near acuity assessment.

Near visual acuity testing uses a standard distance that reflects typical reading tasks. Forty centimeters is chosen because it matches how people usually hold reading material and keeps the accommodative demand around 2.5 diopters, allowing reliable, comparable measurements. Testing much closer, like twenty centimeters, would require about 5 diopters of accommodation and can distort results by stressing focusing ability. Distances such as sixty or one hundred centimeters assess distance or intermediate vision, not near tasks. So forty centimeters is the standard for near acuity assessment.