To study the effect of higher-order aberrations (HOAs) on visual function in keratoconus with a rigid gas permeable (RGP) contact lens (CLs).

Retrospective nonrandomized study.

Thirteen eyes of 10 subjects with keratoconus who wore a RGP CLs (KC-RGP group), 15 eyes of nine normal subjects (normal group), and 14 eyes of nine subjects who wore a RGP CLs (RGP group) who had no ocular diseases except for refractive errors and had 20/20 or better-corrected visual acuity were included in this study. The root-mean-square (RMS) of the third-, fourth-, fifth-, and sixth-order Zernike coefficients (total HOAs), the RMS of the third-order Zernike coefficients (S3) (coma-like aberration), the RMS of the fourth-order coefficients (S4) (spherical-like aberrations), and the area under the log contrast sensitivity function (AULCSF) were evaluated.

The AULCSF in the KC-RGP group was significantly lower than in the other two groups. The total HOAs, S3, and S4 in the KC-RGP group were significantly higher than in the other two groups. There were significant negative correlations between the area under the log contrast sensitivity function and the total HOAs, S3, and S4.

The visual performance in a keratoconic eye with a RGP CLs degrades compared with normal eyes with and without RGP CLs, even if the corrected VA is good. The degradation is assumed to be related to residual HOAs in a keratoconic eye with a RGP CLs.