Stability after laser in situ keratomileusis in moderately and extremely myopic eyes

Abstract

Objective: To evaluate the stability, mechanism, and degree of regression following laser in situ keratomileusis (LASIK) in cases with moderate to extreme myopia after 2 years of follow-up. Setting: Single-center clinical trial. Methods: Fifty-two eyes of 38 patients were enrolled in the study. One year follow-up was available for 47 eyes of 35 patients and 2 year follow-up for 39 eyes of 27 patients. Eyes were divided into 2 groups based on the level of preoperative myopia: Group 1, moderate to high myopia ≥15.0 diopters (D) (range −7.0 to −15.0 D, n=24); Group 2, extreme myopia >15.0 D (range −15.3 to −25.8 D, n=15). Laser in situ keratomileusis was performed using the Chiron Automated Corneal Shaper® microkeratome and the Summit OmniMed excimer laser. Manifest spherical equivalent, mean central keratometry, and central corneal thickness (CCT) were measured preoperatively and 12 and 24 months postoperatively. Results: Group 1 exhibited a mild myopic shift (mean −0.07 ± 0.28 D; P > .2) and a mild increase in keratometry (mean 0.05 ± 0.46 D; P > .6), with an accompanying increase in CCT (mean 7.5 ± 12.2 μm; (P = .006) at 24 months. Group 2 displayed a significant myopic shift (mean −0.7 ± 0.7 D; P = .001) and a significant increase in keratometry (mean 0.4 ± 0.5 D; P = .01), with a mild increase in CCT (mean 2.4 ± 9.7 μm; P = .35) at 24 months. Corneal ectasia was evident in 1 eye in the extreme myopia group. Conclusion: The refractive effect of myopic LASIK up to −15.0 D remained reasonably stable during the second postoperative year. Significant regression of the refractive effect occurred in eyes with higher levels of myopia (>15.0 D), with the risk of progressive ectasia. Extreme caution is recommended when myopic LASIK is performed in eyes with higher levels of myopia.