飞秒激光制瓣LASIK和SBK术后早期角膜后表面高度变化及相关因素分析

摘要

目的 比较飞秒激光制瓣准分子激光角膜原位磨镶术(FS-LASIK)和前弹力层下准分子激光角膜磨镶术(SBK)术后早期角膜后表面高度差值,探讨FS-LASIK术后角膜后表面稳定性及其相关影响因素.方法 采用纵向观察研究设计.纳入2016年1-4月在安徽医科大学第一附属医院接受LASIK的近视及近视散光患者46例91眼,其中FS-LASIK组27例53眼,SBK组19例38眼,分别于术前和术后1d、1周及1个月用Oculyzer系统测量角膜顶点(中央区)和直径2、4、6mm同心圆上(旁中央区、近周边区、周边区)共27个点的角膜后表面高度,比较FS-LASIK和SBK术后早期角膜后表面高度变化. 结果 FS-LASIK组术后1d、1周和1个月角膜后表面中央区高度差分别为(-0.924±1.859)、(-1.151±1.586)和(-0.940±1.994)μm,周边区高度差分别为(1.046±1.667)、(1.172±1.566)和(1.023±1.622) μm,旁中央区和近周边区发生极微后移和前凸;SBK组术后1d、1周和1个月角膜后表面中央区高度差分别为(-0.684±1.454)、(-1.053±1.723)和(-0.553±1.572)μm,周边区高度差分别为(1.207±1.317)、(1.327±1.529)和(1.208±1.415) μm,旁中央区及近周边区发生极微后移和前凸;2个组术后各时间点角膜后表面中央区、旁中央区、周边区和旁周边区高度差比较,差异均无统计学意义(均P＞O.05);FS-LASIK术后1个月角膜后表面中央区及旁中央区只有等效球镜度(SE)、手术切削深度(AD)2个自变量进入回归方程,其他两区域自变量术前角膜中央最薄点厚度(TCT)、SE、AD、剩余角膜基质床厚度(RBT)、切削比(AD/TCT)均未进入回归方程. 结论 FS-LASIK和SBK术后早期角膜后表面顶点发生轻微后移和周边部发生轻微前凸,术后1周时变化最明显,术后1个月时有所恢复.FS-LASIK和SBK术后早期角膜后表面高度均发生轻微变化,但不足以引起角膜扩张,随着预矫正屈光度和AD增加,角膜后表面形态越容易受到影响.%Objective To compare the early change of posterior corneal elevation with femtosecond laser assisted laser in situ keratomileusis (FS-LASIK) and sub-Bowman keratomileusis (SBK) by Oculyzer and analyze the related factors after FS-LASIK.Methods A longitudinal observational study was designed.Ninety-one eyes of 46 patients with myopia or myopic astigmatism in the First Affiliated Hospital of Anhui Medical University from January to April in 2016 were divided into FS-LASIK group (53 eyes of 27 patients),SBK group (38 eyes of 19 patients)according to the patients' wishes and each part of corneal elevation change values were explored after FS-LASIK and SBK surgeries.The posterior corneal elevation was measured at twenty-seven measuring points along the central,paracentral,midperipheral and peripheral zone (vertex and 1,2 and 3 mm radius) using Oculyzer preoperatively,l day,7 days and 1 month postoperatively,respectively.Written informed consent was obtained from each patient before the surgery.Results In the FS-LASIK group,the posterior corneal elevation difference values in the central zone were (-0.924± 1.859),(-1.151 ± 1.586) and (-0.940 ± 1.994) μm 1 day,7 days and 1 month postoperatively,respectively.In the periphery zone,the elevation difference values were (1.046 ± 1.667),(1.172 ± 1.566) and (1.023±1.622)μm.In the paracentral and midperipheral zone,the cornea displayed slightly backward or forward shift.In SBK group,the posterior corneal elevation difference values of the ve,ex were (-0.684 ± 1.454),(-1.053 ±1.723) and (-0.553 ± 1.572) μm 1 day,7 days and 1 month after operation,respectively.In the paracentral and midperipheral zone displayed the same trend with FS-LASIK group,and in the periphery,the values were (1.207 ±1.317),(1.327 ± 1.529) and (1.208 ± 1.415) μm.There were no statistically significant differences in posterior corneal elevation between the two surgery modes among the three time points (all at P ＞ O.05).At 1 month postoperatively,only two independent variables,which were spherical equivalent (SE) and ablation depth (AD)entered the regression in the central and paracentral zones.Independent variables,such as central thinnest corneal thickness (TCT),SE,AD,residual bed thickness (RBT) and the ratio of AD and TCT (AD/TCT) did not enter the regression in other two areas.Conclusions The posterior corneal elevation in the central 6 mm area shows tiny change in the early stage and the variation is larger 7 days after operation in the two groups,but it does not result in keratectasia.With the increase of SE and AD,the posterior corneal elevation is more likely to be affected.