Effects of Scleral Stiffness Properties on Optic Nerve Head Biomechanics
Effects of Scleral Stiffness Properties on Optic Nerve Head Biomechanics
复制标题
DOI：
10.1007/s10439-009-9879-7
复制
发表时间：
2010-04-01
影响因子：
3.8
通讯作者：
Ethier, C. Ross
中科院分区：
文献类型：
--
作者：
Eilaghi, Armin;Flanagan, John G.;Ethier, C. Ross
视神经乳头内的生物力学环境在青光眼中很重要，很大程度上取决于巩膜生物力学特性。在这里，我们使用眼睛有限元 (FE) 模型中一系列测量的非线性巩膜应力-应变关系来计算三个眼压 (IOP) 水平下视神经乳头的生物力学环境。从取自 10 只眼睛的 30 个巩膜样本中选择了与测量的人体巩膜硬度的第 5、50 和 95 个百分位数一致的三种应力-应变关系，并使用超弹性五参数 Mooney-Rivlin 材料模型在眼睛的通用有限元模型中实现。视神经乳头组织内的计算应变在很大程度上取决于巩膜特性，其中大部分差异发生在顺应性和中值情况之间。此外，即使在正常眼压下，应变的幅度也很大（在 15 毫米汞柱下，筛板中的应变幅度高达 5.25%），即使在正常眼压水平下，也比之前报道的值更大。我们得出的结论是，巩膜“脆弱”但仍在生理范围内，将导致视神经乳头应变明显增加，并可能代表青光眼性视神经病变的危险因素。视神经乳头区域变形的估计，特别是在眼压升高时，应考虑巩膜硬度的非线性性质。
The biomechanical environment within the optic nerve head, important in glaucoma, depends strongly on scleral biomechanical properties. Here we use a range of measured nonlinear scleral stress-strain relationships in a finite element (FE) model of the eye to compute the biomechanical environment in the optic nerve head at three levels of intraocular pressure (IOP). Three stress-strain relationships consistent with the 5th, 50th and 95th percentiles of measured human scleral stiffness were selected from a pool of 30 scleral samples taken from 10 eyes and implemented in a generic FE model of the eye using a hyperelastic five-parameter Mooney-Rivlin material model. Computed strains within optic nerve head tissues depended strongly on scleral properties, with most of this difference occurring between the compliant and median scenarios. Also, the magnitudes of strains were found to be substantial even at normal IOP (up to 5.25% in the lamina cribrosa at 15 mmHg), being larger than previously reported values even at normal levels of IOP. We conclude that scleras that are "weak", but still within the physiologic range, will result in appreciably increased optic nerve head strains and could represent a risk factor for glaucomatous optic neuropathy. Estimations of the deformation at the optic nerve head region, particularly at elevated IOP, should take into account the nonlinear nature of scleral stiffness.