For testing binoc accommodative facility in adults, where should reading material be placed, and what distance should be used for an amplitude of 10 D?

For testing binoc accommodative facility in adults, where should reading material be placed, and what distance should be used for an amplitude of 10 D?

• A. 24 cm
• B. 22 cm
• C. 20 cm
• D. 26 cm

Answer: (B)

In binocular accommodative facility testing, you want a near reading distance that provides a moderate accommodative demand so the patient can quickly shift focus with lens flips while maintaining clear, single vision. A distance of about 22 cm yields roughly 4.5 diopters of accommodation demand, which sits well within a typical adult’s amplitude (around 10 D) and allows efficient testing of both accommodation and relaxation with ± lenses. This mid-range demand makes it easier to observe how quickly and accurately the patient can switch focus, without pushing them to the extremes of too much or too little demand. Among common near distances, 22 cm best balances comfort and diagnostic usefulness, whereas closer distances (like 20 cm) impose higher demand and farther distances (like 26 cm) reduce demand, both of which can lessen the test’s sensitivity. For an amplitude of 10 D, the important idea is to choose a reading distance that provides a workable near demand to test facility, not the full amplitude distance itself.

In binocular accommodative facility testing, you want a near reading distance that provides a moderate accommodative demand so the patient can quickly shift focus with lens flips while maintaining clear, single vision. A distance of about 22 cm yields roughly 4.5 diopters of accommodation demand, which sits well within a typical adult’s amplitude (around 10 D) and allows efficient testing of both accommodation and relaxation with ± lenses. This mid-range demand makes it easier to observe how quickly and accurately the patient can switch focus, without pushing them to the extremes of too much or too little demand. Among common near distances, 22 cm best balances comfort and diagnostic usefulness, whereas closer distances (like 20 cm) impose higher demand and farther distances (like 26 cm) reduce demand, both of which can lessen the test’s sensitivity. For an amplitude of 10 D, the important idea is to choose a reading distance that provides a workable near demand to test facility, not the full amplitude distance itself.