Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Mechanical Engineering, University of Texas Rio Grande Valley, Edinburg TX, USA.
Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh PA, USA.
Acta Biomater. 2024 Feb;175:123-137. doi: 10.1016/j.actbio.2023.12.034. Epub 2023 Dec 24.
The optic nerve head (ONH) region at the posterior pole of the eye is supported by a fibrous structure of collagen fiber bundles. Discerning how the fibrous structure determines the region biomechanics is crucial to understand normal physiology, and the roles of biomechanics on vision loss. The fiber bundles within the ONH structure exhibit complex three-dimensional (3D) organization and continuity across the various tissue components. Computational models of the ONH, however, usually represent collagen fibers in a homogenized fashion without accounting for their continuity across tissues, fibers interacting with each other and other fiber-specific effects in a fibrous structure. We present a fibrous finite element (FFE) model of the ONH that incorporates discrete collagen fiber bundles and their histology-based 3D organization to study ONH biomechanics as a fibrous structure. The FFE model was constructed using polarized light microscopy data of porcine ONH cryosections, representing individual fiber bundles in the sclera, dura and pia maters with beam elements and canal tissues as continuum structures. The FFE model mimics the histological in-plane orientation and width distributions of collagen bundles as well as their continuity across different tissues. Modeling the fiber bundles as linear materials, the FFE model predicts the nonlinear ONH response observed in an inflation experiment from the literature. The model also captures important microstructural mechanisms including fiber interactions and long-range strain transmission among bundles that have not been considered before. The FFE model presented here advances our understanding of the role of fibrous collagen structure in the ONH biomechanics. STATEMENT OF SIGNIFICANCE: The microstructure and mechanics of the optic nerve head (ONH) are central to ocular physiology. Histologically, the ONH region exhibits a complex continuous fibrous structure of collagen bundles. Understanding the role of the fibrous collagen structure on ONH biomechanics requires high-fidelity computational models previously unavailable. We present a computational model of the ONH that incorporates histology-based fibrous collagen structure derived from polarized light microscopy images. The model predictions agree with experiments in the literature, and provide insight into important microstructural mechanisms of fibrous tissue biomechanics, such as long-range strain transmission along fiber bundles. Our model can be used to study the microstructural basis of biomechanical damage and the effects of collagen remodeling in glaucoma.
视神经头（ONH）位于眼球后极的区域，由胶原纤维束的纤维结构支撑。辨别纤维结构如何决定该区域生物力学特性对于理解正常生理学以及生物力学在视力丧失中的作用至关重要。ONH 结构内的纤维束表现出复杂的三维（3D）组织和在各种组织成分之间的连续性。然而，ONH 的计算模型通常以均匀化的方式表示胶原纤维，而不考虑它们在组织之间的连续性、纤维之间的相互作用以及纤维结构中的其他纤维特异性效应。我们提出了一种视神经头的纤维有限元（FFE）模型，该模型纳入了离散的胶原纤维束及其基于组织学的 3D 组织，以研究作为纤维结构的视神经头生物力学。FFE 模型是使用猪 ONH 冷冻切片的偏光显微镜数据构建的，该数据使用梁单元表示巩膜、硬脑膜和软脑膜中的单个纤维束，并将管组织表示为连续结构。FFE 模型模拟了胶原束的组织学面内取向和宽度分布以及它们在不同组织之间的连续性。将纤维束建模为线性材料，FFE 模型预测了文献中报道的膨胀实验中观察到的非线性 ONH 响应。该模型还捕获了重要的微观结构机制，包括纤维相互作用和束间的长程应变传递，这些机制以前尚未被考虑。本文提出的 FFE 模型提高了我们对纤维胶原结构在 ONH 生物力学中的作用的理解。
视神经头（ONH）的微观结构和力学特性对于眼部生理学至关重要。组织学上，ONH 区域表现出复杂的、连续的胶原纤维束纤维结构。了解纤维胶原结构对 ONH 生物力学的作用需要以前无法获得的高保真计算模型。我们提出了一种包含基于偏光显微镜图像的组织学纤维胶原结构的 ONH 计算模型。模型预测与文献中的实验结果一致，并提供了对纤维组织生物力学中重要微观结构机制的深入了解，例如纤维束之间的长程应变传递。我们的模型可用于研究生物力学损伤的微观结构基础以及青光眼过程中胶原重塑的影响。
