Improvement of visual acuity and corneal physiology in keratoconus by fitting aspherical, high oxygen-permeable contact lenses

Effect of higher-order aberrations on visual function in keratoconic eyes with a rigid gas permeable contact lens

PURPOSE

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

DESIGN

Retrospective nonrandomized study.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Fitting of aspheric high gas-permeable rigid contact lenses to scarred corneas

Scarring of the cornea often results in an irregular corneal surface, which causes scattering in light perception. Therefore, the impaired visual acuity cannot be adequately corrected by spectacles in most cases. In this study, high oxygen-transmissible aspheric rigid lenses were fitted, with computer assistance, in 26 scarred eyes of 23 consecutive patients. In 15 of 26 eyes (57.7%), a successful fitting with good vision, no complications, and a sufficiently long wearing time was accomplished. The main lens-related complications included fluorescein-staining epithelial defects in five of 26 eyes (19.2%) and epithelial edema in two of 26 eyes (7.7%). Computer-aided fitting was of limited value because keratometer readings were not measurable in 50% of the cases. The results of this study indicate that the application of high oxygen-transmissible aspheric rigid contact lenses may obviate corneal surgery.