What are the results of a flat lens?

• A. Decreased movement and improved centration
• B. Stable centration and comfort
• C. Excessive movement, poor centration, decreased comfort
• D. No change in comfort

Answer: (C)

When a lens is flat, it sits loosely on the cornea because its base curve is not tight enough to match the eye’s contour. This loose fit allows the lens to move more with each blink and can cause it to decenter off the pupil. That combination—excessive movement and poor centration—often leads to vision fluctuations and discomfort, especially as the edge may lift or rub the eyelids. So the best description of a flat lens’s effect is excessive movement, poor centration, and decreased comfort. The other possibilities describe a lens that fits too tightly or is ideal, which would not match the loose, unstable behavior of a flat fit.