近视眼患者LASIK和LASEK术后角膜后表面变化的比较研究

目的探讨近视眼LASIK及LASEK术后角膜后表面变化的差异及意义。方法随机选取近视眼准分子激光患者72例143眼,根据患者接受手术方式的不同分成LASIK组(简称IK组)和LASEK组(简称EK组),根据术后剩余角膜基质床厚度/术前角膜厚度(residual corneal stroma thickness/cornea thickness,RCST/CT)的不同将IK组患者分为IK-I组(RCST/CT<55%;15例30眼)、IK-II组(55%≤RCST/CT<60%;17例34眼)和IK-III组(RCST/CT≥60%;19例38眼),EK组(21例41眼)RCST/CT均≥60%。分别于术前、术后1个月、3个月和6个月应用Oculyzer眼前节分析系统检测角膜后表面高度差异(difference posterior elevation,Diff)值的变化。结果 IK组与EK组术后角膜后表面均向前膨隆。IK-I组术后1个月时Diff值为34.15±24.73,3个月、6个月时分别为28.15±24.82和29.19±23.54,术后1个月与3个月、6个月相比差异均有统计学意义(均为P<0.05),3个月和6个月比较差异无统计学意义(P>0.05)。IK-II组和K-III组术后各时间点角膜后表面Diff值分别为22.59±11.00、22.63±14.08、22.36±14.96和18.72±10.37、18.72±11.93、17.22±10.47,组内比较差异均无统计学意义(均为P>0.05)。术后不同时间点IK-I组和IK-III组比较角膜后表面Diff的差异均有统计学意义(均为P<0.05),IK-I组和IK-II组、IK-II组和IK-III组间比较差异均无统计学意义(均为P>0.05)。EK组术后1个月、3个月和6个月时角膜后表面Diff值分别为14.41±10.44,13.73±10.41和14.72±12.31,同术前相比差异均有统计学意义(均为P<0.05),但术后各时间点间比较差异均无统计学意义(均为P>0.05)。术后不同时间点IK-III组和EK组Diff值的变化差异均无统计学意义(均为P>0.05)。结论 LASIK及LASEK术后角膜后表面均有膨隆,术后RCST/CT越大,对角膜后表面膨隆的影响越小。RCST/CT可以作为临床评估准分子激光角膜屈光手术安全性的重要指标。

Comparison of posterior corneal surface after LASIK and LASEK in myopia

Objective To discuss the changes of posterior corneal surface after laser in situ keratomileusis(LASIK) and laser subepithelial keratomileusis(LASEK) in myopia.Methods Seventy-two cases(143 eyes) were divided into LASIK group(IK group) and LASEK group(EK group).LASIK group was divided into three groups according to the ratio of residual corneal stroma thickness to corneal thickness(RCST/CT),which were IK-I group(RCST/CT were less than 55%,15 cases,30 eyes),IK-II group(RCST/CT were from 55% to 60%) and IK-III group(RCST/CT were equal to or more than 60%).RCST/CT in LASEK group were equal to or more than 60%.The changes of posterior elevation difference(Diff) were obtained by Oculyzer at pre-operation,postoperative 1 month,3 months and 6 months.Results The posterior corneal surface in IK group and EK group had shifted forward generally after LASIK and LASEK.The Diff value of IK-I group at postoperative 1 month,3 months and 6 months were 34.15±24.73,28.15±24.82 and 29.19±23.54,there were statistical differences between 1 months and 3 months,6 months(both P<0.05),and no statistical difference between 3 months and 6 months(P>0.05).Diff value at postoperative time points in IK-II group were 22.59±11.00,22.63±14.08 and 22.36±14.96,which in IK-III group were 18.72±10.37,18.72±11.93 and 17.22±10.47,there was no statistical difference between two groups(both P>0.05).There were statistical difference in Diff value at different time points between IK-I group and IK-III group(both P<0.05),and no statistical difference between IK-I group and IK-II group,IK-II group and IK-III group(both P>0.05).Diff value at postoperative 1 month,3 months and 6 months in EK group were 14.41±10.44,13.73±10.41 and 14.72±12.31,there were statistical difference compared with pre-operation(both P<0.05),but no statistical difference between each postoperative time point(both P>0.05).There was no statistical difference in Diff value at postoperative different time points between IK-III group and EK group(both P>0.05).Conclusion The corneal ectasia appear after LASIK and LASEK,the more RCST/CT has the less effect on the posterior corneal ectasia.RCST/CT can be set as the index to clinical evaluate the safety of laser corneal refractive surgery.