目的：评估飞秒激光小切口角膜基质透镜取出术(SMILE)术中不同角膜帽厚度对术后1 a内角膜光密度(CD)、视觉质量和角膜生物力学的影响，并探讨其安全性。

方法：采用前瞻性随机双眼对照设计，分别于同一接受手术的近视患者两眼实施薄帽(110-120 μm)与厚帽(130-140 μm)SMILE术。术后1 wk，1、3、6 mo及1 a复查CD值、裸眼视力(UDVA)、最佳矫正视力(CDVA)、对比敏感度、波前像差及角膜生物力学等指标，使用线性混合效应模型进行统计分析。

结果：最终60例(120眼，薄帽组和厚帽组各60眼)患者均顺利完成手术并按时复查，平均年龄26.3±3.8岁，其中男34例(57%)，女26例(43%)。薄帽组计划帽厚为115.24±3.10 μm，厚帽组为135.28±3.45 μm，两组透镜厚度及切削量均差异显著(P<0.001)，而残余基质床(RSB)厚度相近(P=0.301)。中央0-6 mm CD值随时间显著下降(P<0.001)，薄帽组整体高于厚帽组(P<0.001)，自术后1 wk至1 a差异持续显著(经Bonferroni校正后P<0.05)。1 a时前层及中间层CD值差异最突出(均P<0.05)，后层无显著差异。厚帽组术后UDVA提升明显(P=0.002)，对比敏感度更优(校正后P<0.05)，薄帽组则在高阶像差总均方根(HOA RMS)、球差及彗差各项数值更高(均P<0.05)。角膜生物力学指标(DA、CBI、SSI)组间无差异(均P>0.05)，两组的安全性事件发生率亦相近(P≥0.5)。

结论：RSB相同前提下，较厚的角膜帽可降低前层CD值，改善对比敏感度与高阶像差表现，无明显生物力学及安全性风险增加，值得作为SMILE术中优选策略。

METHODS: A prospective randomized contralateral controlled design was employed. Thin cap(110-120 μm)and thick cap(130-140 μm)SMILE procedures were performed on the two eyes of the same myopic patients undergoing surgery, respectively. Postoperative evaluations at 1 wk, 1, 3, 6 mo, and 1 y included CD, uncorrected distance visual acuity(UDVA), corrected distance visual acuity(CDVA), contrast sensitivity, wavefront aberrations, and corneal biomechanics. A linear mixed-effects model was used for statistical analysis.

RESULTS:A total of 60 patients(120 eyes, 60 eyes in the thin-cap group and 60 eyes in the thick-cap group)completed the surgery successfully and attended scheduled follow-up visits. The mean age was 26.3±3.8 y, including 34 males(57%)and 26 females(43%).The intended cap thickness was 115.24±3.10 μm in the thin-cap group and 135.28±3.45 μm in the thick-cap group. There were significant intergroup differences in lenticule thickness and ablation depth(P<0.001), whereas the residual stromal bed(RSB)thickness was comparable between groups(P=0.301). Central 0-6 mm CD significantly decreased over time(P<0.001), and the thin-cap group had overall higher densitometry values than the thick-cap group(P<0.001), with significant differences persisting from 1 wk to 1 y postoperatively(Bonferroni-corrected P<0.05). At 1 y, significant CD differences were most pronounced in the anterior and central layers(both P<0.05), with no significant differences in posterior layers. The thick-cap group showed a significant improvement in UDVA(P=0.002)and better contrast sensitivity(corrected P<0.05), while the thin-cap group had higher values of total root mean square of higher-order aberrations(HOA-RMS), spherical aberration, and coma(all P<0.05). No statistical differences were observed between groups in corneal biomechanical parameters(DA, CBI, SSI)(all P >0.05), and the incidence of safety events was also comparable between the two groups(P≥0.5).

CONCLUSION: Given an equivalent RSB thickness, thicker corneal caps can reduce anterior-layer CD, improve contrast sensitivity and higher-order aberration outcomes, without obvious increases in biomechanical risks or safety concerns.Therefore, it warrants consideration as a preferred intraoperative strategy for SMILE.