The mechanical properties of the cornea in corneal ectasia disease undergo a significant reduction, yet the alterations in mechanical properties within distinct corneal regions remain unclear. In this study, we established a rabbit corneal ectasia model by employing collagenase II to degrade the corneal matrix within a central diameter of 6 mm. Optical coherence tomography was employed for the in vivo assessment of corneal morphology (corneal thickness and corneal curvature) one month after operation. Anisotropy and viscoelastic characteristics of corneal tissue were evaluated through biaxial and uniaxial testing, respectively. The results demonstrated a marked decrease in central corneal thickness, with no significant changes observed in corneal curvature. Under different strains, the elastic modulus of the cornea exhibited no significant differences in the up-down and naso-temporal directions between the control and model groups. However, the cornea in the model group displayed a significantly lower elastic modulus compared to the control group. Specifically, the elastic modulus of the central region cornea in the model group was significantly lower than that of the entire cornea within the same group. Moreover, in comparison to the control group, the cornea in the model group exhibited a significant increase in both creep rate and overall deformation rate. The instantaneous modulus and equilibrium modulus were significantly reduced in the model cornea. No significant differences were observed between the entire cornea and the central cornea concerning these parameters. The results indicate that corneal anisotropy remains unchanged in collagenase-induced ectatic cornea. However, a significant reduction in viscoelastic properties is noticed. This study provides valuable insights for investigating changes in corneal mechanical properties within different regions of ectatic corneal disease.
扩张性角膜疾病中角膜的力学性能显著降低，但其不同区域力学性能的变化尚不清楚。本文利用Ⅱ型胶原酶降解中央6 mm直径内的角膜基质建立了兔角膜扩张模型，造模1月后采用光学相干断层扫描仪检测在体角膜形态（角膜厚度与角膜曲率）；分别采用双轴和单轴拉伸方法检测整体和中央局部角膜组织的各向异性和粘弹性力学特性。结果表明：术后1月模型组角膜中央厚度显著降低，角膜曲率无显著变化。不同应变下，无论整体还是中央局部角膜，对照组与模型组角膜沿上-下方向与鼻-颞方向的弹性模量差异无统计学意义；模型组弹性模量均显著低于正常对照组；模型组中央角膜弹性模量显著低于模型组整体角膜。与对照组相比，模型组角膜的蠕变率与整体变形率均显著增高，而瞬时模量与平衡模量则显著降低；但整体角膜与中央局部角膜各参数之间均无显著差异。本文结果提示，胶原酶处理引起角膜扩张后未导致角膜各向异性特征发生改变，但粘弹性力学性能显著下降。本研究为探究扩张性角膜疾病不同区域角膜力学性能变化规律提供了参考。.
Keywords: Anisotropy; Corneal ectasia; Creep; Viscoelasticity.