Department of Ophthalmology, Casey Eye Institute, Oregon Health & Science University, Portland, OR, USA.
Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA.
Acta Biomater. 2023 Jul 1;164:346-362. doi: 10.1016/j.actbio.2023.04.008. Epub 2023 Apr 16.
The aqueous humor actively interacts with the trabecular meshwork (TM), juxtacanalicular tissue (JCT), and Schlemm's canal (SC) through a dynamic fluid-structure interaction (FSI) coupling. Despite the fact that intraocular pressure (IOP) undergoes significant fluctuations, our understanding of the hyperviscoelastic biomechanical properties of the aqueous outflow tissues is limited. In this study, a quadrant of the anterior segment from a normal human donor eye was dynamically pressurized in the SC lumen, and imaged using a customized optical coherence tomography (OCT). The TM/JCT/SC complex finite element (FE) with embedded collagen fibrils was reconstructed based on the segmented boundary nodes in the OCT images. The hyperviscoelastic mechanical properties of the outflow tissues' extracellular matrix with embedded viscoelastic collagen fibrils were calculated using an inverse FE-optimization method. Thereafter, the 3D microstructural FE model of the TM, with adjacent JCT and SC inner wall, from the same donor eye was constructed using optical coherence microscopy and subjected to a flow load-boundary from the SC lumen. The resultant deformation/strain in the outflow tissues was calculated using the FSI method, and compared to the digital volume correlation (DVC) data. TM showed larger shear modulus (0.92 MPa) compared to the JCT (0.47 MPa) and SC inner wall (0.85 MPa). Shear modulus (viscoelastic) was larger in the SC inner wall (97.65 MPa) compared to the TM (84.38 MPa) and JCT (56.30 MPa). The conventional aqueous outflow pathway is subjected to a rate-dependent IOP load-boundary with large fluctuations. This necessitates addressing the biomechanics of the outflow tissues using hyperviscoelastic material-model. STATEMENT OF SIGNIFICANCE: While the human conventional aqueous outflow pathway is subjected to a large-deformation and time-dependent IOP load-boundary, we are not aware of any studies that have calculated the hyperviscoelastic mechanical properties of the outflow tissues with embedded viscoelastic collagen fibrils. A quadrant of the anterior segment of a normal humor donor eye was dynamically pressurized from the SC lumen with relatively large fluctuations. The TM/JCT/SC complex were OCT imaged and the mechanical properties of the tissues with embedded collagen fibrils were calculated using the inverse FE-optimization algorithm. The resultant displacement/strain in the FSI outflow model was validated versus the DVC data. The proposed experimental-computational workflow may significantly contribute to understanding of the effects of different drugs on the biomechanics of the conventional aqueous outflow pathway.
房水通过动态流固耦合与小梁网（TM）、管周组织（JCT）和施莱姆氏管（SC）积极相互作用。尽管眼压（IOP）会发生显著波动，但我们对房水流出组织的超粘弹性生物力学特性的理解还很有限。在这项研究中，从正常供体眼球的前节象限中动态加压 SC 管腔，并使用定制的光相干断层扫描（OCT）进行成像。基于 OCT 图像中的分段边界节点，重建了嵌入胶原纤维的 TM/JCT/SC 复合体有限元（FE）。使用反向 FE 优化方法计算了嵌入粘弹性胶原纤维的流出组织细胞外基质的超粘弹性力学特性。此后，使用光相干显微镜构建了同一供体眼的 TM、相邻 JCT 和 SC 内壁的 3D 微结构 FE 模型，并从 SC 管腔施加流加载边界。使用 FSI 方法计算流出组织的变形/应变，并与数字体积相关（DVC）数据进行比较。TM 的剪切模量（0.92 MPa）大于 JCT（0.47 MPa）和 SC 内壁（0.85 MPa）。SC 内壁的剪切模量（粘弹性）（97.65 MPa）大于 TM（84.38 MPa）和 JCT（56.30 MPa）。传统的房水流出途径受到具有大波动的依赖于速率的 IOP 加载边界的影响。这需要使用超粘弹性材料模型来解决流出组织的生物力学问题。意义声明：虽然人类传统的房水流出途径受到大变形和时变 IOP 加载边界的影响，但我们不知道有任何研究计算过嵌入粘弹性胶原纤维的流出组织的超粘弹性力学特性。从 SC 管腔以相对较大的波动对正常供体眼的前节象限进行动态加压。对 TM/JCT/SC 复合体进行 OCT 成像，并使用反向 FE 优化算法计算组织的粘弹性特性。FSI 流出模型中的位移/应变结果与 DVC 数据进行了验证。所提出的实验计算工作流程可能会极大地促进对不同药物对传统房水流出途径生物力学影响的理解。
