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

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 oculyzer 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. Key words: Corneal aberrations; Keratomileusis; Photorefractive keratectomy; Optical quality