准分子激光原位角膜磨镶术后角膜后表面前突的影响因素

目的 描述准分子激光原位角膜磨镶术(LASIK)后角膜后表面前突并探讨影响其前突程度的因素.方法 前瞻性系列病例研究.2006年12月至2007年2月在华中科技大学同济医学院附属协和医院眼科行LASIK手术患者82例(通过3年的观察,无一例出现圆锥角膜),其中男38例,女44例,年龄18～44岁,平均(24.2±5.5)岁,取右眼数据进行分析.采用OrbscanⅡz、Goldman眼压计、超声角膜测厚仪分别测量这82眼手术前后角膜地形图、眼压以及角膜厚度.采用t检验和Pearson相关分析与线性回归等统计学方法.结果 ①LASIK术后角膜后表面最佳拟合球面半径缩短(113.32±66.87) μm,平均前突(71.97±28.70)μm,术前术后角膜后表面曲率差为(0.93±0.54)D.②LASIK手术后角膜后表面都有不同程度轻微前突,其程度与术前眼压呈正相关(r=0.461,P＜0.01);与术后角膜瓣下残余基质厚度呈负相关(r=-0.453,P＜0.01).③在36个月观察中,无一例发生角膜扩张,但术后角膜后表面都不同程度向前突出.结论 角膜后表面前突是LASIK术后角膜变薄的必然反应,其程度与术前眼压呈正相关,与术后角膜瓣下残余基质厚度呈负相关.

Factors affecting the forward shift of the posterior corneal surface in laser in situ keratomileusis

Objective To investigate the forward shift of the posterior corneal surface and related influential factors after laser in situ keratomileusis (LASIK).Methods It was a prospective case series study.Eighty-two patients with myopia (38 males and 44 females) who had undergone LASIK at Union Hospital between December 2006 and February 2007 were retrospectively reviewed.The average age was 24.2±5.5 years,ranging from 18 to 44 years.No case of keratoconus was found during 3 years of follow-up.Intraocular pressure,corneal thickness and topography measurements were obtained with a Goldmann tonometer,ultrasonic corneal pachymeter and Orbscan Ⅱ z before and after surgery.All surgery was performed by the same surgeon using a 217Z100 Bausch & Lomb.Results After LASIK,the best fit sphere radius of the posterior corneal surface was shortened by 113.32±66.87 μm,with an average forward shift of 71.97±28.70 μm.The difference in the posterior corneal surface power between pre-and post-operation was 0.93±0.54 D.The forward shift of the posterior corneal surface showed a positive correlation with preoperative intraocular pressure (r=0.461,P＜0.01),and a negative correlation with residual stromal bed thickness (r=-0.453,P＜0.00).There was a forward shift of varying degrees in the posterior comeal surface in most cases,including several severe cases.But no corneal ectasia was observed during the follow-up period of 36 months.Conclusion The forward shift of the posterior corneal surface could be an inevitable response because of corneal thinning after LASIK,and a change in the posterior corneal surface showed a positive correlation with preoperative intraocular pressure and a negative correlation with residual stromal bed thickness.