In gradient AC/A, Δvergence/ΔAccommodation expresses which relation?

In gradient AC/A, Δvergence/ΔAccommodation expresses which relation?

• A. The change in accommodation per diopter of vergence
• B. The change in vergence per diopter of accommodation
• C. The change in vergence per prism diopter
• D. The change in accommodation per prism diopter

Answer: (B)

Gradient AC/A captures how much the eyes converge when the amount of accommodation changes. Accommodation is measured in diopters, vergence in prism diopters, so the ratio is expressed as the change in vergence per unit change in accommodation. In other words, how many prism diopters of vergence result from a 1 diopter change in accommodation. That’s why the correct phrial description is the change in vergence per diopter of accommodation. If, for example, the gradient AC/A is around a few prism diopters per diopter, a 1 D shift in accommodation would produce that much additional vergence. The other phrasing would describe the reciprocal or involve different units, which isn’t what gradient AC/A measures.

Gradient AC/A captures how much the eyes converge when the amount of accommodation changes. Accommodation is measured in diopters, vergence in prism diopters, so the ratio is expressed as the change in vergence per unit change in accommodation. In other words, how many prism diopters of vergence result from a 1 diopter change in accommodation. That’s why the correct phrial description is the change in vergence per diopter of accommodation. If, for example, the gradient AC/A is around a few prism diopters per diopter, a 1 D shift in accommodation would produce that much additional vergence. The other phrasing would describe the reciprocal or involve different units, which isn’t what gradient AC/A measures.