What is the recommended action when flexure occurs?

What is the recommended action when flexure occurs?

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

Answer: (A)

Flexure happens when the GP lens deforms under eyelid and tear-film forces because it’s too flexible or its back surface is too steep for the eye. The most effective fix is to make the lens more resistant to bending: flatten the back surface curvature to reduce the posterior surface’s tendency to bend against the cornea, and increase the central thickness to stiffen the lens overall. A flatter base curve lowers the bending moments at the posterior interface, while a thicker lens increases rigidity, so it holds its shape during blinking and maintains stable vision. Other adjustments like changing the overall diameter or sag aren’t as directly aimed at stopping that deformation, so they’re not the preferred remedy in this situation.

Flexure happens when the GP lens deforms under eyelid and tear-film forces because it’s too flexible or its back surface is too steep for the eye. The most effective fix is to make the lens more resistant to bending: flatten the back surface curvature to reduce the posterior surface’s tendency to bend against the cornea, and increase the central thickness to stiffen the lens overall. A flatter base curve lowers the bending moments at the posterior interface, while a thicker lens increases rigidity, so it holds its shape during blinking and maintains stable vision. Other adjustments like changing the overall diameter or sag aren’t as directly aimed at stopping that deformation, so they’re not the preferred remedy in this situation.