Effects of collagen microstructure and material properties on the deformation of the neural tissues of the lamina cribrosa

摘要

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 mu m) and microscale (0.73 mu m) resolutions. Mesoscale fiber-aware FE models were first used to calculate ONH deformations at an lOP 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 to 12%. Pores near the sclera] 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 these patterns are determined by the underlying structure and geometry of the LC beams and pores. To the best of our knowledge, this is the first computational model that reproduces the highly heterogeneous neural tissue strain fields observed experimentally.