Decreasing center thickness of a GP lens will cause lens flexure to:

• A. Lower flexure
• B. No change
• C. Higher flexure
• D. Depends on anterior edge

Answer: (C)

Shortening the center thickness reduces the lens’s bending stiffness, so the GP lens bends more easily under the same forces from blinking and the tear film. The optic zone acts like a curved plate, and bending stiffness rises with thickness, roughly with thickness cubed. When center thickness is decreased, the lens becomes more pliable and deforms more to fit the corneal surface, increasing flexure. This greater flexure can momentarily alter the curvature and effective power of the lens. The other options don’t fit because thicker lenses resist bending more (lower flexure), there would be a change with altered thickness (no change isn’t accurate), and the effect is driven by the center thickness rather than the anterior edge design.