Geometric Customization of Optical and Transition Zone Parameters for Treatment of Compound Myopic Astigmatism With the NIDEK EC-5000 Excimer Laser

Abstract

To compare the refractive outcome of two ablation zone designs using LASIK for the correction of compound myopic astigmatism. This retrospective study compared refractive outcomes in two groups of patients undergoing LASIK. In the circular treatment group, 45 eyes were corrected with circular optical and transition zones of 6 mm and 6.5 mm, respectively. In the customized treatment group, 45 eyes were corrected with optical and transition zones enlarged along the flat axis to 6.5 mm and 7.5 mm, respectively. P values <.05 were considered statistically significant. Mean preoperative spherical equivalent refraction was -5.36+/-2.02 diopters (D) and -5.36+/- 2.13 D for the circular and customized treatment groups, respectively. Mean postoperative spherical equivalent refraction was -0.09+/-0.74 D and -0.11+/-0.42 D for the circular and customized treatment groups, respectively. Mean cylinder was 0.49+/-0.39 D and 0.22+/-0.43 D for the circular and customized treatment groups, respectively (P<.001). Postoperative blur strength index was 0.68+/-0.44 D and 0.39+/-0.27 D in the circular and customized treatment groups, respectively (P<.001). Uncorrected visual acuity was significantly better in the customized treatment group compared with the circular treatment group (P<.05). The gain in lines of best spectacle-corrected visual acuity was significantly greater in the customized treatment group compared with the circular treatment group (P<.001). An elliptical ablation zone for treating compound myopic astigmatism results in better efficacy, safety, and lower tissue removal than a circular treatment zone. This may be due to the geometric optimization provided by the enlargement of the optical and transition zones along the flat meridian.