Postoperative Changes in Corneal Morphology and Posterior Corneal Elevation of High Myopia Corrected by Femtosecond LASIK Combined with Accelerated Corneal Cross-Linking
1Shandong University of Traditional Chinese Medicine, Jinan 250014, China 2Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, Shandong Clinical Medicine Research Center, Jinan 250002, China
Abstract：Objective: To investigate the alternation of corneal morphology and posterior corneal elevation after femtosecond laser-assisted laser in situ kerafomileusis (FS-LASIK) combined with accelerated corneal cross-linking surgery for the correction of high myopia. Methods: This was a retrospective case-control study. Patients with high myopia who received FS-LASIK Xtra or FS-LASIK alone in the Affiliated Eye Hospital of Shandong University of Traditiond Chinese Medicine from July 2020 to April 2022 were continuously enrolled in this study. Participants in this study included 46 patients (92 eyes) in the FS-LASIK Xtra group and 41 patients (82 eyes) in the FS-LASIK alone group. Diopter of patients before and 1, 3 and 6 months after surgery was collected. Mean curvature (Km) and posterior corneal elevation (PCE) in the central area (corneal apex), paracentral area (the 2 mm circle with the apex as the center), and midperipheral area (the 4 mm circle with the apex as the center) were recorded before and 1, 3 and 6 months after surgery. Preoperative refractive index, central corneal thickness, and intraoperative ablation depth were also recorded. The alternation of corneal posterior corneal elevation (?PCE) was the difference between the preoperative height and the postoperative height at 6 months. Independent sample t-test or Mann Whitney U-test were used to compare the differences between the two groups, the alternations of PCE at different time points before and after surgery were analyzed using repeated measures of variance. Results: The Km of the FS-LASIK group and the FS-LASIK Xtra group before surgery was 43.40 ± 1.11 D and 43.59 ± 1.09 D, respectively, with no statistically significant difference (P>0.05). The corneal curvature of the two groups was stable and no statistically signifcant difference (all P>0.05) at each time point after surgery. There was no statistically significant difference in the PCE between the two groups before surgery (all P>0.05). At 6 months after surgery, the PCE in the central region of the FS-LASIK group and FS-LASIK Xtra group were 1.00 (0, 2.00) μm and 0 (-1.00, 2.00) μm, showing a statistically signifcant difference (Z=-2.31, P=0.021). At 3 months after operation, the PCE in the near peripheral area of FS-LASIK group and FS-LASIK Xtra group was -1.00(-2.00, 0) μm and -0.50 (-1.25, 0.50) μm, respectively, and the difference was statistically significant (Z=-2.86, P=0.004); at 6 months after surgery, the values were -1.13 (-2.00, 0) μm and -0.25 (-1.00, 0.44) μm, respectively, with statistical significance (Z=-2.74, P=0.006). The postoperative ?PCE in the central region of the FS-LASIK group and FS-LASIK Xtra group were -0.50 (-2.00, 1.00) μm and -1.00 (-2.00, 0) μm, respectively, and the difference was statistically significant (Z=-2.58, P=0.010). And the postoperative ?PCE in the paracentral region was -0.25 (-0.75, 0.25) μm and -0.50 (-1.25, 0) μm, respectively, with statistical significance (Z=-2.96, P=0.003). Conclusions: After FS-LASIK and FS-LASIK Xtra correction for high myopia, the posterior corneal elevation of the cornea in the central and paracentral regions slightly shifted back, and the near peripheral region slightly protruded. The FS-LASIK Xtra group showed significant alternations and tended to stabilize at 3 months after surgery. During the observation period, the two surgical methods for correcting high myopia are safe and effective, and the combination of accelerated corneal cross-linking is more conducive to the stability of the posterior corneal elevation.
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