Comparison of Anterior and Posterior Corneal Surface Change after Laser In Situ Keratomileusis and Laser Epithelial Keratomileusis

ABSTRACT

PURPOSE: To compare the time course of the change in corneal surface between LASIK and LASEK groups, which show the difference in residual bed thickness. METHODS: Twenty-one eyes of 15 patients who underwent LASIK and 20 eyes of 12 patients who underwent LASEK were included in this study and were evaluated on a review retrospectively. Corneal topography was performed preoperatively, 1 week, 2 months, 6 months, and 1 year postoperatively. The change in corneal surface was measured with the Orbscan II. The change in the elevation of the anterior corneal surface was assessed using the difference map produced from the first postoperative week and the subsequent postoperative maps. The elevation of the posterior corneal surface was measured using the difference map generated from the preoperative and postoperative elevation maps. RESULTS: After LASIK and LASEK, the posterior corneal surface was shifted anteriorly by 18.87 +/- 5.91 micrometer and 28.77 +/- 15.46 micrometer at 1 week, 15.43 +/- 6.49 micrometer and 16.03 +/- 11.32 micrometer at 2 months, 15.58 +/- 6.19 micrometer and 15.14 +/- 7.17 micrometer at 6 months, and 16.38 +/- 6.67 micrometer, 12.81 +/- 9.94 micrometer at 1 year, respectively. Compared to the 1 week postoperative measurement, average posterior corneal surface in the LASIK group reduced by 3.44 micrometer at 1 year (p=.175) ; in the LASEK group, it reduced by 23.24 micrometer at 1 year (p=.020). CONCLUSIONS: In conclusion, in both groups, the posterior corneal surface shifted forward in the early time point postoperatively, and thereafter, it showed a trend toward gradual progressive backward shift over time, but not to the preoperative levels. The elevation of the posterior corneal surface was reduced relatively more in LASEK than in LASIK at 1 year after surgery.