Flatter than "K," on "K," steeper than "K": does the cornea know the difference?

Twenty-nine subjects were fitted with PMMA contact lenses of equal overall diameter, optical zone diameter, and z-value in a double-masked clinical trial. Five different treatment groups were analyzed and a one-way analysis of variance was used to determine whether significant differences in corneal thickness change existed between the treatment groups. Lenses fitted 1 D flatter than "K" caused the least amount of corneal thickness change.