It is widely considered that intraocular pressure (IOP)-induced deformation within the neural tissue pores of the lamina cribrosa (LC) contributes to neurodegeneration and glaucoma. Our goal was to study how the LC microstructure and mechanical properties determine the mechanical insult to the neural tissues within the pores of the LC. Polarized light microscopy was used to measure the collagen density and orientation in histology sections of three sheep optic nerve heads (ONH) at both mesoscale (4.4 µm) and microscale (0.73 µm) resolutions. Mesoscale fiber-aware FE models were first used to calculate ONH deformations at an IOP of 30 mmHg. The results were then used as boundary conditions for microscale models of LC regions. Models predicted large insult to the LC neural tissues, with 95th percentile 1st principal strains ranging from 7–12%. Pores near the scleral boundary suffered significantly higher stretch compared to pores in more central regions (10.0 ± 1.4% vs. 7.2 ± 0.4%; p=0.014; mean ± SD). Variations in material properties altered the minimum, median, and maximum levels of neural tissue insult but largely did not alter the patterns of pore-to-pore variation, suggesting thesepatterns are determined by the underlying structure and geometry of the LC beamsand pores. To the best of our knowledge, this is the first computational modelthat reproduces the highly heterogeneous neural tissue strain fields observedexperimentally.
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机译:人们普遍认为,眼内压(IOP)诱发的筛板(LC)的神经组织孔内变形会导致神经变性和青光眼。我们的目标是研究LC的微结构和机械性能如何确定对LC孔内神经组织的机械损伤。偏光显微镜用于在中尺度(4.4 µm)和微米(0.73 µm)分辨率下测量三个绵羊视神经头(ONH)的组织学切片中的胶原密度和方向。中尺度的光纤感知有限元模型首先用于计算在30 mmHg的IOP下的ONH变形。然后将结果用作LC区域微观模型的边界条件。模型预测会对LC神经组织造成很大的侮辱,第95个百分位数的1 st sup>主应变范围为7–12%。与更中心区域的孔相比,巩膜边界附近的孔具有明显更高的拉伸度(10.0±1.4%对7.2±0.4%; p = 0.014;平均值±SD)。材料特性的变化改变了神经组织损伤的最小,中值和最大水平,但在很大程度上并未改变孔-孔变化的模式,表明这些图案由LC光束的基本结构和几何形状确定和毛孔。据我们所知,这是第一个计算模型再现观察到的高度异质性神经组织应变场实验上。
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