Schwaner Stephen A, Feola Andrew J, Ethier C Ross
George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
J R Soc Interface. 2020 Apr;17(165):20190695. doi: 10.1098/rsif.2019.0695. Epub 2020 Apr 1.
Glaucoma is the leading cause of irreversible blindness and is characterized by the death of retinal ganglion cells, which carry vision information from the retina to the brain. Although it is well accepted that biomechanics is an important part of the glaucomatous disease process, the mechanisms by which biomechanical insult, usually due to elevated intraocular pressure (IOP), leads to retinal ganglion cell death are not understood. Rat models of glaucoma afford an opportunity for learning more about these mechanisms, but the biomechanics of the rat optic nerve head (ONH), a primary region of damage in glaucoma, are only just beginning to be characterized. In a previous study, we built finite-element models with individual-specific rat ONH geometries. Here, we developed a parametrized model of the rat ONH and used it to perform a sensitivity study to determine the influence that six geometric parameters and 13 tissue material properties have on rat optic nerve biomechanical strains due to IOP elevation. Strain magnitudes and patterns in the parametrized model generally matched those from individual-specific models, suggesting that the parametrized model sufficiently approximated rat ONH anatomy. Similar to previous studies in human eyes, we found that scleral properties were highly influential: the six parameters with highest influence on optic nerve strains were optic nerve stiffness, IOP, scleral thickness, the degree of alignment of scleral collagen fibres, scleral ground substance stiffness and the scleral collagen fibre uncrimping coefficient. We conclude that a parametrized modelling strategy is an efficient approach that allows insight into rat ONH biomechanics. Further, scleral properties are important influences on rat ONH biomechanics, and additional efforts should be made to better characterize rat scleral collagen fibre organization.
青光眼是不可逆性失明的主要原因，其特征是视网膜神经节细胞死亡，这些细胞将视觉信息从视网膜传递至大脑。尽管生物力学是青光眼疾病进程的重要组成部分这一观点已被广泛接受，但生物力学损伤（通常由于眼压升高）导致视网膜神经节细胞死亡的机制仍不清楚。青光眼大鼠模型为深入了解这些机制提供了契机，但青光眼主要损伤部位大鼠视神经乳头（ONH）的生物力学特性才刚刚开始被研究。在之前的一项研究中，我们构建了具有个体特异性大鼠ONH几何形状的有限元模型。在此，我们开发了一种大鼠ONH参数化模型，并利用它进行敏感性研究，以确定六个几何参数和13种组织材料特性对眼压升高引起的大鼠视神经生物力学应变的影响。参数化模型中的应变大小和模式与个体特异性模型的应变大小和模式总体匹配，这表明参数化模型充分近似了大鼠ONH的解剖结构。与之前对人眼的研究类似，我们发现巩膜特性具有高度影响力：对视神经应变影响最大的六个参数分别是视神经刚度、眼压、巩膜厚度、巩膜胶原纤维排列程度、巩膜基质刚度和巩膜胶原纤维解卷曲系数。我们得出结论，参数化建模策略是一种有效的方法，能够深入了解大鼠ONH的生物力学特性。此外，巩膜特性对大鼠ONH生物力学有重要影响，应进一步努力更好地表征大鼠巩膜胶原纤维的组织结构。
