It is widely accepted that biomechanics plays an important role in glaucoma pathophysiology, but the mechanisms involved are largely unknown. Rats are a common animal model of glaucoma, and finite element models are being developed to provide much-needed insight into the biomechanical environment of the posterior rat eye. However, material properties of rat ocular tissues, including the sclera, are currently unknown. Since the sclera plays a major role in posterior ocular biomechanics, our goal was to use inverse finite element modeling to extract rat scleral material properties. We first used digital image correlation to measure scleral surface displacement during whole-globe inflation testing. We modeled the sclera as a nonlinear material with embedded collagen fibers and then fit modeled displacements to experimental data using a differential evolution algorithm. Subject-specific models were constructed in which 3 parameters described the stiffness of the ground substance and collagen fibers in the posterior eye, and 16 parameters defined the primary orientation and alignment of fibers within eight scleral sub-regions. We successfully extracted scleral material properties for eight rat eyes. Model displacements recreated general patterns of the experimental displacements but did not always match local patterns. The fiber directions and fiber concentration parameters were highly variable, but on average, fibers were aligned circumferentially and were more aligned in the peripapillary sclera than in the peripheral sclera. The material properties determined here will be used to inform future finite element models of the rat posterior eye with the goal of elucidating the role of biomechanics in glaucoma pathophysiology.

中文翻译：

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用逆有限元建模获得的大鼠巩膜的生物力学特性。

人们普遍认为，生物力学在青光眼病理生理学中起着重要作用，但所涉及的机制在很大程度上是未知的。大鼠是一种常见的青光眼动物模型，正在开发有限元模型以提供对大鼠后眼生物力学环境急需的洞察。然而，包括巩膜在内的大鼠眼组织的材料特性目前尚不清楚。由于巩膜在后眼部生物力学中起着重要作用，我们的目标是使用逆有限元建模来提取大鼠巩膜材料特性。我们首先使用数字图像相关性来测量全球膨胀测试期间的巩膜表面位移。我们将巩膜建模为嵌入胶原纤维的非线性材料，然后使用差分进化算法将模拟位移与实验数据拟合。构建了特定于受试者的模型，其中 3 个参数描述了后眼中基质和胶原纤维的刚度，16 个参数定义了八个巩膜子区域内纤维的主要方向和排列。我们成功提取了八只大鼠眼睛的巩膜材料特性。模型位移重建了实验位移的一般模式，但并不总是与局部模式相匹配。纤维方向和纤维浓度参数变化很大，但平均而言，纤维在圆周上排列，并且在周围巩膜中比在周边巩膜中更排列。