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

Objective: To evaluate the stability, mechanism, and degree of regression f ollowing laser in situ keratomileusis (LASIK) in cases with moderate to ext reme 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 fo r 39 eyes of 27 patients. Eyes were divided into 2 groups based on the leve l of preoperative myopia: Group 1, moderate to high myopia less than or equ al to 15.0 diopters (D) (range -7.0 to -15.0 D, n = 24); Group 2, extreme m yopia > 15.0 D (range -15.3 to -25.8 D, n = 15). Laser in situ keratomileus is was performed using the Chiron Automated Corneal Shaper (R) microkeratom e and the Summit OmniMed excimer laser. Manifest spherical equivalent, mean central keratometry, and central corneal thickness (CCT) were measured pre operatively 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 mum; (P = .006) at 24 m onths, 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 mum; P = .35) at 24 mo nths. 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 re asonably stable during the second postoperative year. Significant regressio n of the refractive effect occurred in eyes with higher levels of myopia (> 15.0 D), with the risk of progressive ectasia. Extreme caution is recommen ded when myopic LASIK is performed in eyes with higher levels of myopia. (C ) 2001 ASCRS and ESCRS.