To counter flexure, which adjustment is recommended?

To counter flexure, which adjustment is recommended?

• A. Flatten BC and increase CT
• B. Steepen BC and decrease CT
• C. Increase OAD
• D. Decrease sag

Answer: (A)

Flexure happens when blinking and lid pressure deform a gas-permeable lens on the eye. To counter it, you want a lens that resists bending—more stiffness and less curvature. Flattening the base curve reduces how curved the lens is, so it resists bending under eyelid forces. Increasing the center thickness boosts rigidity, making the lens harder to deform. Together, these changes help the lens maintain its shape and position during blinking, reducing vision fluctuations from flexure. Steepening the base curve or thinning the lens would do the opposite, increasing the tendency to flex. Changes to overall diameter or sag mainly affect edge behavior rather than the core resistance to flexure.

Flexure happens when blinking and lid pressure deform a gas-permeable lens on the eye. To counter it, you want a lens that resists bending—more stiffness and less curvature. Flattening the base curve reduces how curved the lens is, so it resists bending under eyelid forces. Increasing the center thickness boosts rigidity, making the lens harder to deform. Together, these changes help the lens maintain its shape and position during blinking, reducing vision fluctuations from flexure. Steepening the base curve or thinning the lens would do the opposite, increasing the tendency to flex. Changes to overall diameter or sag mainly affect edge behavior rather than the core resistance to flexure.