PURPOSE To investigate the biomechanical properties of the ex vivo human paired corneas after completion of photorefractive keratectomy (PRK) versus small incision lenticule extraction (SMILE) in the same donor. METHODS In this experimental study, 13 pairs of human corneas unsuitable for transplantation were equally divided into two groups. Corneal thickness was measured in each eye directly before laser refractive surgery. Corneas from the right eye were treated with PRK and corneas from the left eye with SMILE. All corneas were subjected to a refractive correction of -10.00 diopters (D) sphere and -0.75 D cylinder at 0° with a 7 mm zone, using either surface ablation (PRK) or 130 µm cap (SMILE). For two-dimensional biomechanical measurements, corneoscleral buttons underwent two testing cycles (preconditioning stress-strain curve from 0.03 to 9.0 N and stress-relaxation at 9.0 N during 120 seconds) to analyze the elastic and viscoelastic material properties. The effective elastic modulus was calculated. Statistical analysis was performed with a confidence interval of 95%. RESULTS In stress-strain measurements, the effective elastic modulus was not significantly different (P = .081) between SMILE (9.58 ± 4.26 MPa) and PRK (11.9 ± 4.90 MPa). The effect size was medium (Cohen's d = 0.58). In stress-relaxation measurements, the remaining stress was not significantly different (P = .878) between SMILE (122 ± 33 kPa) and PRK (123 ± 30 kPa). CONCLUSIONS The lenticule extraction procedure (SMILE) and the surface ablation technique (PRK) may be considered equivalent in terms of biomechanical stability when measured experimentally in ex vivo human fellow eye corneas. [J Refract Surg. 2019;35(8):501-505.].

中文翻译：

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在人眼中，通过二维引伸体外实验测试了人角膜的生物力学特性：PRK与SMILE。

目的研究在同一捐献者中完成光折射角膜切除术（PRK）与小切口小孔镜摘除术（SMILE）后，离体人类配对角膜的生物力学特性。方法在本实验研究中，将13对不适合移植的人角膜平均分为两组。在激光屈光手术之前，直接测量每只眼睛的角膜厚度。右眼的角膜用PRK治疗，左眼的角膜用SMILE治疗。使用表面消融（PRK）或130 µm帽盖（SMILE）对所有角膜进行0°-10.00屈光度（D）球体和-0.75 D圆柱体的屈光矫正，其区域为7 mm。对于二维生物力学测量，角膜巩膜纽扣经历了两个测试周期（预处理​​应力-应变曲线从0.03到9。0 N和120秒内9.0 N的应力松弛）来分析弹性和粘弹性材料的性能。计算有效弹性模量。进行统计分析的置信区间为95％。结果在应力应变测量中，SMILE（9.58±4.26 MPa）和PRK（11.9±4.90 MPa）之间的有效弹性模量没有显着差异（P = .081）。效果大小为中等（Cohen d = 0.58）。在应力松弛测量中，SMILE（122±33 kPa）和PRK（123±30 kPa）之间的残余应力没有显着差异（P = .878）。结论当在离体人眼角膜上进行实验测量时，在生物力学稳定性方面，可以认为小球摘除程序（SMILE）和表面消融技术（PRK）是等效的。[J Refract Surg。2019;