Anterior corneal optical aberrations induced by laser in situ keratomileusis for hyperopia

To evaluate the effects of hyperopic laser in situ keratomileusis (LASIK) on anterior corneal higher-order aberrations (HOAs) (3rd to 6th orders).

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.

In a retrospective study, 3rd-order to 6th-order HOAs from preoperative and 3-month postoperative corneal topographic maps of eyes that had hyperopic LASIK using the Visx Star S2 and Visx Star S3 laser systems were calculated. There were 20 eyes of 14 patients in each group; the optical and transition zones were 6.0 mm and 9.0 mm, respectively. The surgically induced changes in anterior corneal HOAs and the differences between the HOA changes in corneas treated with and without active eye tracking were analyzed.

In both groups, hyperopic LASIK induced a significant reduction in 4th-order spherical aberration (SA) coefficients (Z4(0)) in the 3.0 mm and the 6.0 mm central zones, and the decrease was significantly correlated with increasing hyperopic correction (except in the Visx S3 group's central 3.0 mm zone). In the 6.0 mm zone in both groups, the root-mean-square (RMS) of the SA (Z4(0) and Z6(0)) decreased significantly, whereas there were no significant changes in the total HOAs. By excluding Z4(0), the mean RMS values for the remaining 21 Zernike terms increased by more than 30% (both P<.016). A simulated increase in pupil size from 3.0 to 6.0 mm caused a significantly smaller increase in SA in postoperative corneas compared to the preoperative values. Differences between the S2 and S3 groups were minimal.

Hyperopic LASIK decreased SAs and reduced the magnitude of the SA increase that occurred with pupil dilation. Higher-order aberrations excluding the 4th-order SA increased significantly.