Abstract:AIM:To investigate the clinical effect and safety of laser in situ keratomileusis(LASIK) retreatment for correcting residual ametropia.METHODS:A retrospective study of 72 eyes of 44 cases who had a secondary LASIK procedure was carried out.After a mean follow-up of 13.32±12.06(3-58) months after the primary procedure,the mean myopic residual refraction was -2.56±1.56 diopters (D). The relation of age,center corenal thickness(CCT),corneal flap thickness and the residual stroma thickness of cornea with the residual ametropia were analyzed.RESULTS:The mean uncorrected visual acuity was 0.89± 0.19(0.5 to 1.2)μm,the mean spherical equivalent(SE) was 0.05±0.57D (P <0.05). The partner T test indicated that the CCT before the secondary LASIK,which was 502.69±31.54μm,was thicker than the theory residual CCT 456.08±26.04μm,and the difference was statistically sighificant(t=-0.785,P=0.000). Multivariate regression analysis indicated that the SE of preoperation and the depth of cut have prominence effect on the residual ametropia,the regression equation was residual ametropia =-0.317+0.588×SE+0.031×depth of cut.CONCLUSION:The SE and depth of cut seem to be the main factors for refractive regression. The corneal stroma proliferation is the main mechanism to refractive regression. Secondary LASIK is an effective and safe method to treat residual ametropia after primary LASIK for myopia.
