Objective:To determine the effect of different ablation depths on the curative effect after small incision lenticule extraction (SMILE).Methods:A total of 116 eyes (58 patients w ith anisometropia) that underwent SMILE were included in this retrospective study from April 2016 to July 2017 in Ningbo Yinzhou People's Hospital.The deeper ablated eye in each patient was assigned to Group A,while the contralateral eye was assigned to Group B.Uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA),spherical equivalent (SE),higher-order aberrations (HOA),and other parameters were recorded preoperatively and at 1 day,1 week,1 month,and 6 months postoperatively.The average preoperative corneal curvature,axial length,corrected intraocular pressure,and expected ablation depth were recorded,while the actual ablation depths were calculated.The data were analyzed by repeated measurement ANOVA,paired samples t-tests,Pearson correlation analysis,and linear regression analysis.Results:The mean safety index and the mean effective index were greater than 1.0 in both groups 6 months postoperatively.Mean postoperative SEs were both within the range of ±0.5 diopter (D).The increases of corneal total higher-order aberrations (t=3.747,P=0.001),spherical aberration (t=3.308,P=0.002),and vertical coma (t=3.507,P=0.001) in Group A were all higher than in Group B at 1 month postoperatively.Two cases of diffuse lamellar keratitis occurred in Group A while three occurred in Group B.All were cured by glucocorticoid treatment.The deviations between the expected and actual ablation depths in Group A were greater than that in Group B (t=4.250,P＜0.001).The deviation between the expected and actual ablation depths was correlated with the expected ablation depth (r=0.397,P＜0.001),axial length (r=0.350,P=0.002),and SE (r=-0.308,P=0.007).Using multiple linear regression,the following relationship was determined:D=0.171×expected ablation depth-8.201,where D was the deviation between the expected and actual ablation depths.Conclusions:Within the range of indications,ablation depth did not affect the safety,stability,or effectiveness of SMILE surgery.However,the deeper the expected ablation depth was,the more corneal total HOA,spherical aberration,and vertical coma were introduced after surgery,and the worse the predictability of ablation depth was.The predictability of ablation depth was weakly correlated with expected ablation depth axial length,and preoperative SE.%目的:评估不同切割深度对飞秒激光小切口角膜基质透镜取出术(SMILE)后治疗效果的影响,并初步探讨切割深度可预测性的影响因素.方法:回顾性研究.选择2016年4月至2017年7月在宁波市鄞州人民医院行SMILE的近视屈光参差患者58例(116眼).以预期切割深度较深眼为A组,对侧眼为B组.分别统计患者术前及术后ld、1周、1个月、6个月裸眼视力(UCVA)、最佳矫正视力(BCVA)、等效球镜度(SE)、角膜高阶像差等.记录患者术前平均角膜曲率、眼轴长度、矫正眼压、预期切割深度,并计算实际切割深度.采用重复测量方差分析、配对t检验、Pearson相关分析、多元线性回归分析对数据进行统计分析.结果:术后6个月2组的有效性指数、安全性指数均大于1.0.术后1个月,A组角膜总高阶像差(t=3.747,P=0.001)、球差(t=3.308,P=0.002)、垂直彗差(t=3.507,P=0.001)的增加量较B组大.A、B组分别发生2眼和3眼一级弥漫层间角膜炎,经治疗后均痊愈.A组预期与实际切割深度的差值较B组大(t=4.250,P＜0.001).预期与实际切割深度的差值与预期切割深度(r=0.397,P＜0.001)、眼轴长度(r=0.350,P=0.002)、SE(r=-0.308,P=0.007)均有相关性,通过多元线性回归得到公式:预期与实际切割深度的差值=0.171×预期切割深度-8.201.结论:SMILE适应证范围内,不同切割深度不会影响手术的安全性、稳定性及有效性.预期切割深度较深眼引入的角膜总高阶像差、球差和垂直彗差较大,预期切割深度越深可预测性越差.另外,预期切割深度的可预测性与预期切割深度、眼轴长度、术前SE等呈弱相关性.
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