Base curves for hydrogel soft lenses are generally

• A. Flat
• B. Steep
• C. Neither
• D. Both

Answer: (A)

Base curves for hydrogel soft lenses are generally flatter than the eye’s corneal curvature to promote a comfortable, movable fit. Because these lenses are flexible, a flatter base curve (larger radius) allows the lens to settle with the tear film and move a bit with each blink. This movement helps with tear exchange under the lens and reduces the chance of a tight, uncomfortable fit or lid binding. A steeper base curve would grip the cornea more tightly and can lead to reduced movement and discomfort. In practice, eye care providers favor a flatter base curve as the starting point for most hydrogel soft lens fits, adjusting only if the eye’s curvature is unusually steep or flat.