LASIK术后角膜基质床厚度与后表面前凸相关性研究

Correlation of corneal stroma thickness and corneal posterior surface protrusive values after LASIK

目的研究准分子激光原位角膜磨镶术(laser in situ keratomileusis,LASIK)术后保留角膜基质床厚度(corneal stroma thickness,CST)不同对角膜后表面前凸的影响。方法对接受LASIK术并有术后6个月完整随访记录的50例(94眼)患者,分别于术前及术后1个月、3个月和6个月采用ORBSCAN-Ⅱ角膜地形图检测角膜后表面形态并计算出前凸值,比较各时间点角膜后表面前凸值的变化。按其术后保留CST不同分为:A组13例(25眼),250μm≤CST<300μm;B组25例(48眼),300μm≤CST<350μm;C组12例(21眼),CST≥350μm。比较术后各组角膜后表面前凸值的变化,分析术后CST与角膜后表面前凸的相关性。结果样本总体角膜后表面前凸值术后1个月、3个月、6个月分别为(40.62±14.24)μm、(43.81±17.87)μm、(41.55±13.60)μm,进行单因素方差分析,经比较差异无统计学意义(F=1.69,P=0.18),组间两两比较经SNK检验差异无统计学意义(P=0.17)。术后6个月角膜后表面前凸和术后保留CST相关性分析显示二者呈负线性相关(r=0.59,P<0.01)。术后6个月各组角膜后表面前凸值分别为:A组(47.28±12.36)μm,B组(38.29±14.29)μm,C组(24.80±9.44)μm,C组前凸值小于前2组,各组间差异有统计学意义(F=23.48,P<0.01),组间两两比较SNK检验差异均有统计学意义(P均<0.05)。结论LASIK术后角膜后表面前凸与保留CST呈负线性相关,当保留CST≥350μm时角膜后表面稳定性显著增加。

Objective To evaluate the effect of different reserved residual corneal stroma thickness（CST） on corneal posterior surface protrusion after laser in situ keratomileusis（LASIK）. Methods Protrusive values of 50 cases （94 eyes ）, which received LASIK and had complete following up records of 6 months postoperative, were calculated after measuring the shape of corneal posterior surface with ORBSCAN- Ⅱ corneal topography preoperative, at 1 month, 3 months and 6 months postoperative. The changes of protrusive values at corneal posterior surface were compared among different time points. The patients were divided into 3 groups based on the residual CST： Group A（13 cases,25 eyes）,CST with 250 μm to 300 μm;Group B（25 cases,48 eyes）, CST with 300 μm to 350 μm;Group C（ 12 cases,21 eyes） ,CST with more than 350 μm. Changes of corneal posterior surface protrusion were compared among different groups postoperative. The correlation of postoperative CST and corneal posterior surface protrusion was analyzed. Results Total protrusive values of corneal posterior surface was（40.62± 14.24） μm, （43.81± 17.87） μm and （41.55 ± 13.60） μm at postoperative 1 month, 3 months and 6 months, respectively. There was no significant difference among them with One-way ANOVA（ F = 1.69 ,P =0. 18 ）, either between each pair with SNK test （P = 0.17 ）. The residual CST negatively correlated with corneal posterior surface protrusion at 6 months postoperative （r = 0. 59, P 〈 0. 01 ）. At postoperative 6 months, the protrusive values of corneal posterior surface were（47. 28 ± 12.36） μm, （38.29 ± 14. 29） μm and（24.80 ±9.44）μm in group A,B and C,respectively. The value of group C was lower than that of group A or B, and there was significant difference among them （F =23.48,P 〈 0.01 ）. There was statistical difference between each two groups with SNK test （ all P 〈 0.05 ）. Conclusion After LASIK, corneal posterior surface protrusion negatively correlates with reserved residual CST, and there is significant increase of stability of corneal posterior surface when the reserved residual CST is 350 μm or more.