True or False: It is safe to dispense lenses that are too flat or too steep.

• A. True
• B. False
• C. Not sure
• D. Depends on the case

Answer: (B)

Proper fit is essential for gas permeable lenses because the lens must sit on the eye in a way that centers well, allows a stable optical |tear film| interface, and provides comfortable movement with each blink. If a GP lens is too flat, it sits too loosely on the cornea, tends to decenter, and shows edge lift; vision can be unstable and tear exchange under the lens becomes inconsistent, which can lead to dryness, glare, and reduced wearing time. If the lens is too steep, it bears too much on the cornea, restricting movement and causing bearing, corneal indentation or staining, redness, and discomfort; this also disrupts tear flow and can increase hypoxic stress on the cornea. In either scenario, comfort, vision, and corneal health are at risk, so dispensing lenses that are too flat or too steep is not safe. The appropriate action is to adjust the fit—changing the base curve, diameter, or design—to achieve a well-centered, stable fit with good movement and tear exchange.