低、中、高度近视患者行SMILE的角膜切削精确性研究

Accuracy of Central Corneal Ablation in Small Incision Lenticule Extraction for Low, Moderate and High Myopia

目的研究不同近视程度患者飞秒激光小切口基质透镜取出术（SMILE）后中央角膜切削误差及其变化趋势,探讨不同近视程度对切削误差的影响.方法：回顾性病例对照研究.选取2017 年1-8 月于温州医科大学附属眼视光医院行SMILE的近视患者61 例（120 眼）,将其按术前屈光度分为低度（24眼,-0.50 D≤低度近视≤-3.00 D）、中度（54眼,-3.00 D 〈中度近视≤-6.00 D）以及高度（42眼,高度近视〉 -6.00 D）近视组.于术前、术后1 个月、3 个月使用Sirius眼前节分析系统测量中央角膜厚度（CCT）并计算切削误差及中央角膜切削偏差率,其中切削误差定义为中央角膜实际切削厚度（A-CCT）与预测切削厚度（P-CCT）的差值（△CCT）,中央角膜切削偏差率定义为△CCT 与P-CCT的比值.采用配对t检验、单因素方差分析、Kruskal-Wallis H检验以及Pearson相关分析对数据进行分析.结果：各组患者中央角膜实际切削厚度均小于预测切削厚度;术后1 个月和3 个月各组间△CCT差异有统计学意义（F=21.047、35.100,均P 〈 0.001）;各组间中央角膜切削偏差率差异无统计学意义.在末次检查时,其中低、中、高度近视组△CCT分别为（-8.9±5.0）μm、（-15.6±6.2）μm、（-21.4±5.9）μm,3 组A-CCT与P-CCT差异均有统计学意义（t =8.67、18.50、23.65,P 〈 0.001）.术后切削误差与术前屈光度、切削直径呈正相关（r =0.649、0.384,均P 〈 0.001）,与术前CCT呈负相关（r=-0.219,P=0.016）.结论：各近视组A-CCT均小于P-CCT;不同近视患者SMILE手术后中央角膜切削误差随着近视程度的增大而增大,但各组间中央角膜切削偏差率保持一致.

Objective： To study ablation error and its central corneal thickness variations in patients with myopiaafter small incision lenticule extraction （SMILE）, and to investigate the influence of low, moderate andhigh myopia on central corneal ablation error. Methods： This was a retrospective case-control study.Sixty-one myopic patients （a total of 120 eyes） who had undergone SMILE surgery from January 2017 toAugust 2017 at the Eye Hospital of Wenzhou Medical University were chosen for the study. Data wereorganized by refractive status into low （24 eyes, -0.50 D≤low myopia≤-3.00 D）, moderate （54 eyes,-3.00 D 〈 moderate myopia ≤-6.00 D）, and high （42 eyes, high myopia 〉 -6.00 D） myopia groups.The central corneal thickness （CCT） of patients undergoing SMILE was measured by the Sirius anteriorsegment analysis system preoperatively and postoperatively at 1 month and 3 months. Among differentmyopia groups, the ablation error was calculated simultaneously during each visit and was defined as thedifference （△CCT） between actual central corneal ablation thickness （A-CCT） and the predicted centralcorneal thickness （P-CCT）. The difference ratio of △CCT （defined as △CCT/P-CCT） and the relationship（in diopters） between △CCT, CCT, and ablation diameter were analyzed. Data were analyzed with apaired-samples t-test, ANOVA, Kruskal-Wallis H test, and Pearson correlation analysis. Results： Amongthe three myopia groups, results for A-CCT were all less than the P-CCT, and the differences in △CCTbetween any two groups were found to be statistically significant （F=21.047, 35.100, all P 〈 0.001）. Nosignificant difference was found in the difference ratios of △CCT among the three groups. The △CCTsof the low, moderate, and high myopia groups were -8.9 ± 5.0 μm, -15.6 ± 6.2 μm, -21.4 ± 5.9 μm,respectively. The differences between A-CCT and P-CCT were significant （t=8.67, 18.50, 23.65,P 〈 0.001）. Moreover, there were significant correlations both in the relationship of corneal ablation errorwith preoperative refractive status and ablation diameter after SMILE surgery （r=0.649, 0.384, all P 〈 0.001）.However, SMILE surgical ablation error and preoperative corneal thickness had a negative correlation（r=-0.219, P=0.016）. Conclusions： A-CCT in low, moderate and high myopia groups after SMILEsurgery is less than the predicted thickness. △CCT increases as the degree of myopia increases. Thereare significant differences in △CCT between different myopia groups, nevertheless the difference ratio of△CCT basically remains consistent.