LASIK术后5年内角膜后表面曲率和中央角膜厚度变化

A five-year follow-up study of posterior corneal curvature and central corneal thickness after LASIK using Orbscan Ⅱ

目的采用0rbscan Ⅱ角膜地形图仪对准分子激光原位角膜磨镶术（LASIK）后角膜后表面曲率和中央角膜厚度进行5年随访测量，探索其变化规律。方法回顾性系列病例研究。LASIK手术患者48例（48眼），平均屈光度（-6．25±2．87）D。术前及术后1个月、3个月、6个月、9个月、1年、2年、3年、5年，采用0rbscanⅡ测量其角膜后表面曲率（中央6mm区域）和角膜厚度。采用重复测量的方差分析和LSD法比较角膜后表面曲率和中央角膜厚度的变化，并对两者关系作Pearson相关分析。结果①角膜后表面曲率变化：术后1个月，角膜后表面曲率较术前升高（t=8．21l，P〈0．01）；术后1-9个月，数值无明显变化，前后差异无统计学意义；术后9个月至2年，角膜后表面曲率逐渐下降，前后比较差异有统计学意义（t=4．640、-2．659，P均〈0．叭）；2年后，角膜后表面曲率趋于稳定，前后差异均无统计学意义。②中央角膜厚度变化：术后1个月，中央角膜厚度较术前下降（t=10．08，P〈0．01）；术后1-9个月，中央角膜厚度逐渐上升，前后差异有统计学意义（t=5．402、-4．428、-2．334，P均〉0．05）；术后9个月，中央角膜厚度趋于稳定，前后差异无统计学意义。（3）LASIK术后角膜后表面曲率与中央角膜厚度呈负相关（r=0．703，P〈0．01）。结论LASIK术后早期角膜后表面中央区前凸，中央角膜厚度增加，此后两者均趋于稳定。随访期内角膜后表面曲率与中央角膜厚度呈负相关。

Objective To study the long-term （five-year follow-up） changes in posterior corneal curvature and central corneal thickness by using the Orbscan Ⅱtopographer in patients who had undergone laser in situ keratomileusis （LASIK） for myopia. Methods Forty-eight eyes of 48 patients who had undergone LASIK for myopia were included in a retrospective observational case series study. The mean preoperative refractive error was -6.25：t：2.87 D. The preoperative and postoperative changes in the posterior corneal curvature and central corneal thickness of each eye were measured by Orbscan Ⅱ. The posterior corneal curvature was obtained from the central 6mm zone of the Orbscan Ⅱ. The postoperative follow-up period was at 1, 3, 6, 9, 12, 24, 36 and 60 months. Using SPSS 16.0 software, a comparison of the least-significant difference （LSD） pairwise was used to analyze the difference in the posterior corneal curvature and central corneal thickness at each follow-up visit. Results （1）The posterior corneal curvature was higher in the 1st month postoperatively compared to preoperative curvature （t=8.211, P〈0.01）. There was no statistically significant difference for the change in posterior corneal curvature from the 1st month to the 9th month （P〉0.05）. The posterior corneal curvature slowly decreased over time from the 9th month to the 24th month （the values of t were --4.640 and -2.659, the values of P were 〈0.001 and 0.014）. The posterior corneal curvature did not become stable until after the 24th month （/9〉0.05）. （2）The central corneal thicknesswas lower in the 1st month postoperatively than preoperative thickness （t=10.08, P〈0.01）. The central corneal thickness slowly increased over time from the 1st month to the 9th month （the values of t were -5.402, -4.428 and -2.334, the values of P were 〈0.001, 〈0.001 and 0.027）. The central corneal thickness did not become stable until after the 9th month （P〉0.05）. （3）The posterior corneal curvature was correlated with corneal thickness （r=-0.703, P〈0.01）. Conclusion The posterior corneal curvature and the central corneal thickness both increase shortly after LASIK surgery and stabilize after this initial period. There is a negative correlation between posterior corneal curvature and central corneal thickness.