Aberrations and visual performance following standard laser vision correction

Abstract

Purpose: To relate the change of ocular aberrations with the change of visual performance produced by standard laser in situ keratomileusis (LASIK) for myopia.

Methods: Aberrations and visual performance were measured before and after surgery in 22 eyes. Total aberrations were measured using a laser ray tracing technique. Corneal aberrations were obtained using a commercial videokeratoscope and custom software. Visual performance was evaluated in terms of best spectacle-corrected contrast sensitivity and high-contrast visual acuity.

Results: The amount of total and corneal aberrations increased with LASIK in all except two eyes. In general, the total and corneal aberration patterns were well-correlated after LASIK. However, the anterior corneal surface alone did not capture all the information (ie, possible changes induced on the posterior corneal surface or interactions between the different ocular components), which suggests that total aberrations are better predictors of visual performance. The decrease of the modulation transfer function (both in terms of area under the curve or as a function of spatial frequency) with LASIK accounted for most of the decrease in contrast sensitivity. High-resolution visual acuity was not very sensitive to the LASIK-induced changes in image quality.

Conclusion: Wavefront and total aberration measurements, and in particular a combination of the two techniques, provide useful information for understanding the optical changes induced by standard refractive surgery. Predictions of the change in modulation transfer function derived from wave aberrations matched measurements of change in contrast sensitivity.