Which statement about optic zone diameter and lens fit is true?

• A. Increasing the optic zone diameter makes the lens fit steeper
• B. Increasing the optic zone diameter makes the lens fit flatter
• C. The optic zone diameter has no effect on lens fit
• D. The optic zone diameter only affects movement

Answer: (B)

Optic zone diameter is the central area of the GP lens that sits over the cornea. When you increase this central zone, more of the corneal surface is covered by the lens center and the transition from the central zone to the peripheral curves shifts outward. This redistribution tends to reduce the need for a steep posterior surface in the periphery, so the lens settles with less apical bearing and less edge lift. In practical terms, a larger optic zone diameter often results in a flatter seating on the cornea. It’s not correct that it has no effect, or that it only affects movement; changing the optic zone diameter changes how the lens aligns with the cornea, influencing the fit as well as centration.