If flexure occurs, what adjustment should be made to the GP lens?

If flexure occurs, what adjustment should be made to the GP lens?

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

Answer: (A)

Flexure happens when a GP lens bends under the forces of blinking and the vacuum between the lens and cornea. To stop or reduce this bending, you want to lessen the suction and make the lens more rigid. Flattening the base curve reduces the inner curvature, which lowers the suction that tends to pull the lens into the cornea and bend it. Increasing the center thickness makes the lens stiffer, so it resists deformation during blinking. Together, these adjustments address both the cause of flexure (suction) and the lens’s ability to bend, giving a more stable fit. Steepening the base curve would increase suction and encourage more flexure. Decreasing center thickness reduces rigidity, allowing more bending. Increasing the overall diameter mainly affects edge alignment instead of central flexure, and decreasing sag alters central thickness in a way that doesn’t reliably reduce flexure.

Flexure happens when a GP lens bends under the forces of blinking and the vacuum between the lens and cornea. To stop or reduce this bending, you want to lessen the suction and make the lens more rigid. Flattening the base curve reduces the inner curvature, which lowers the suction that tends to pull the lens into the cornea and bend it. Increasing the center thickness makes the lens stiffer, so it resists deformation during blinking. Together, these adjustments address both the cause of flexure (suction) and the lens’s ability to bend, giving a more stable fit.

Steepening the base curve would increase suction and encourage more flexure. Decreasing center thickness reduces rigidity, allowing more bending. Increasing the overall diameter mainly affects edge alignment instead of central flexure, and decreasing sag alters central thickness in a way that doesn’t reliably reduce flexure.