In this study, we established an experimental human corneal stroma model of simulated cornea tissue composed of thin anterior cornea strips layers obtained from small incision lenticular extraction (SMILE) surgery. We investigated the biomechanical effect of ultraviolet-A- riboflavin cross-linking at different depths of corneal stroma model and correlated it with stromal microstructural changes examined by transmission electron microscopy (TEM). Corneal strips were harvested from fresh human corneal lenticules obtained after SMILE surgery. Experimental models (n = 34) were established by superimposing the corneal lenticule strips until their thickness reached close to 500 μm. Corneal cross-linking (CXL) was performed subsequently using standard or accelerated protocol. Elasticity and viscosity were quantified using stress-strain extensometer. TEM was used to visualize the collagen fiber diameter and interfibrillar spacing. The relative change in Young's modulus (rel. ΔE) decreased nonlinearly with increasing stromal depth both in the standard and accelerated groups. Compared to the sham controls, the rel. ΔE in standard and accelerated CXL groups increased significantly in the anterior 400 μm and 275 μm depth, respectively. Also, the relative change in stress (rel. ΔS) was significantly lower after standard and accelerated CXL compared to sham controls. Depth analysis showed similar results for the elastic effect. TEM images showed a small, non-significant increase in fibril diameter. The interfibrillar spacing decreased significantly after standard and accelerated CXL in the anterior-mid stromal region. We noted that the increase of corneal stiffness correlated with decrease in interfibrillar spacing after CXL. The stiffening effect was depth dependent. The effect of accelerated CXL was less in the deep corneal stromal regions compared to standard CXL.

在这项研究中，我们建立了一个模拟的角膜组织的实验性人类角膜基质模型，该模型由小切口双凸透镜提取（SMILE）手术获得的薄的前角膜条层组成。我们研究了紫外线-A-核黄素交联在角膜基质模型不同深度的生物力学效应，并将其与通过透射电子显微镜（TEM）检测的基质微结构变化相关联。从SMILE手术后获得的新鲜人角膜微孔中收获角膜带。实验模型（n = 34）是通过叠加角膜微孔带直至其厚度接近500μm来建立的。随后使用标准或加速方案进行角膜交联（CXL）。弹性和粘度使用应力应变引伸计定量。用TEM观察胶原纤维的直径和纤维间的间距。在标准组和加速组中，杨氏模量的相对变化（相对ΔE）都随着基质深度的增加而非线性减小。与假控件相比，rel。标准CXL组和加速CXL组的ΔE分别在前400μm和275μm深度显着增加。同样，与假对照组相比，标准和加速CXL后的相对应力变化（相对ΔS）明显更低。深度分析显示出相似的弹性效果结果。TEM图像显示原纤维直径小而无明显增加。在前中基质区标准和加速CXL后，原纤维间间距显着降低。我们注意到，CXL后角膜刚度的增加与原纤维间间距的减少有关。加强效果取决于深度。与标准CXL相比，深层角膜基质区域CXL加速的影响较小。