True or False: Peripheral curve radii/widths are important for peripheral clearance because they help determine lens position and comfort.

• A. False
• B. Not important
• C. Irrelevant
• D. True

Answer: (D)

Peripheral curve design on a gas permeable lens shapes how the edge sits around the cornea and lid anatomy. This edge geometry controls where the lens ends up on the eye and how tear fluid flows at the periphery. The radii and widths of these peripheral curves determine whether the edge sits snugly without rubbing, or binds too tightly, or lifts too much. Proper peripheral clearance means there’s a stable tear reservoir under the edge and a smooth interface with the lid during blinking. This reduces friction, supports tear exchange under the edge, and helps keep the lens in a stable position as the eye moves. Because the periphery largely governs fit, position, and comfort, these dimensions are indeed important for peripheral clearance.