Which statement describes the unit used for amplitude of accommodation in the Half Amp Method?

Which statement describes the unit used for amplitude of accommodation in the Half Amp Method?

• A. Meters
• B. Diopters
• C. Radians
• D. Lumenes

Answer: (B)

Amplitude of accommodation is the amount the eye can change its optical power to shift focus from distant to near. That change is a measure of refractive power, so its unit is diopters, the unit that expresses optical power (D = 1/m). In the Half Amp Method, you estimate this range by measuring the near point distance and using AA ≈ 1/NP (in meters). For example, a near point at 0.5 m corresponds to about 2 diopters of accommodation. Other units like meters, radians, or lumens don’t quantify the eye’s focusing power, so diopters is the appropriate unit.

Amplitude of accommodation is the amount the eye can change its optical power to shift focus from distant to near. That change is a measure of refractive power, so its unit is diopters, the unit that expresses optical power (D = 1/m). In the Half Amp Method, you estimate this range by measuring the near point distance and using AA ≈ 1/NP (in meters). For example, a near point at 0.5 m corresponds to about 2 diopters of accommodation. Other units like meters, radians, or lumens don’t quantify the eye’s focusing power, so diopters is the appropriate unit.