Development of an advanced nomogram for myopic astigmatic wavefront-guided laser in situ keratomileusis (LASIK).

BACKGROUND AND

OBJECTIVE

To identify the relationship between preoperative parameters and postoperative overcorrection or undercorrection in eyes with myopic astigmatism treated with wavefront-guided laser in situ keratomileusis (LASIK), and to develop an advanced surgical nomogram.

PATIENTS AND

METHODS

A retrospective chart review of 468 eyes that underwent wavefront-guided LASIK for myopia with astigmatism with the Alcon LADARVision 4000 (Alcon Laboratories, Fort Worth, TX), of which 235 had flaps created by microkeratome (OneUse; Moria Surgical, Doylestown, PA) and 233 by femtosecond laser (Intralase; AMO, Santa Ana, CA). Manifest sphere, cylinder, and spherical equivalent were recorded preoperatively and 3 months postoperatively. Various parameters from patient records were analyzed to identify which had greatest influence on outcomes.

RESULTS

Manifest spherical equivalent was the most important predictor of surgical overcorrection, with the second being spherical aberration. In both groups, there was a statistically significant (P < .0001) correlation of spherical aberration with the amount of overcorrection. Using these two parameters, compensatory nomograms were derived.

CONCLUSION

Surgical overcorrection in wavefront-guided LASIK for myopic astigmatism correlates positively with the amount of spherical equivalent treated and preoperative spherical aberration. Nomograms incorporating spherical aberration may improve accuracy of outcomes.