LASIK与LASEK术后角膜前后表面像差的变化

Changes in aberrations on the anterior and posterior corneal surfaces after laser in situ keratomileusis and laser-assisted subepithelial keratectomy

目的探讨准分子激光原位角膜磨镶术（LASIK）与准分子激光上皮下角膜切削术（LASEK）手术前后角膜前、后表面球差（C球）、彗差（C彗）、三叶草像差（C三）和总高阶像差（C高）的变化。方法前瞻性病例对照研究。应用Oculyzer眼前节分析系统采集并计算LASIK组17例（34眼）、LASEK组17例（34眼）患者的角膜前后表面的各像差。对检查结果进行方差分析、独立样本t检验和Pearson相关分析。结果LASIK组角膜前表面C球、C高在术后1个月和3个月时均较术前有明显增加，术后1个月和3个月时比较差异无统计学意义；EASEK组角膜前表面C球、C彗和C高在术后1个月和3个月时均较术前有明显增加，术后1个月和3个月时比较差异无统计学意义；术后1个月时LASIK组的角膜前表面C球和C高高于LASEK组，术后3个月仍呈现同样趋势，而角膜前表面C彗始终低于LASEK组，C三差异无统计学意义；术后LASIK组角膜前表面C球和C高的增高值（△C球、△C高）高于LASEK组，而C彗和C三的变化在两组之间差异无统计学意义；角膜前表面△C球和△C高与矫正的等效球镜度呈现显著的正相关关系；两种术式间、同种术式手术前后角膜后表面各像差值差异无统计学意义。结论LASIK和LASEK术后角膜前表面的C球、C彗和C高会增大，且在术后3个月时尚无明显恢复；到术后3个月，角膜前表面△C球和△C高在LASIK组始终高于LASEK组，而这种变化与所矫正等效球镜度呈正相关；两种术式对角膜后表面的各像差均无影响。

Objective To compare changes in wavefront aberrations on the anterior and posterior corneal surfaces after laser in situ keratomileusis （LASIK） and laser-assisted subepithelial keratectomy （LASEK） for myopia, especially for spherical aberrations, coma, trefoil and total higher order aberrations. Methods A prospective study was designed for 68 eyes of 34 patients who had undergone LASIK and LASEK. The patients were divided into 2 groups according to the procedure used. An oeulyzer analytical system was used to measure corneal aberrations before and after surgery. Data were analyzed using ANOVA, independent samples t test and pearson correlation. Results One and 3 months after surgery, spherical aberrations and total higher-order aberrations of the anterior corneal surface in the LASIK group increased （P〈0.01）, but the differences at 1 month and 3 months were not significant （P〉0.05）. The same results occurred in the LASEK group for spherical aberrations, coma and total higher-order aberrations of the anterior corneal surface. Spherical aberrations and total higher-order aberrations of the anterior corneal surface were higher in the LASIK group than in the LASEK group 1 month after surgery （P〈0.01）, and the same tendency was found 3 months after surgery. However, coma aberrations on the anterior corneal surface in the LASIK group were less than those in the LASEK group at any time after surgery （P〈0.05）. No differences were found in trefoil aberrations on the anterior corneal surface during both procedures （P〉0.05）. Furthermore, the amount of correction achieved was positively correlated to these changes. Wavefront aberrations on the posterior corneal surface remained constant with both procedures and there were no differences when the procedures were compared （P〉0.05）. Conclusion Spherical aberrations, coma and total higher-order aberrations on the anterior corneal surface increased after both procedures, and did not recover until the 3 month after surgery. The changes in spherical aberrations and total higher-order aberrations on the anterior corneal surface were higher in the LASIK group than in the LASEK group, and depended on correction achieved in both procedures. The two procedures had no effect on wavefront aberrations on the posterior corneal surface.