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Ian C Campbell, Baptiste Coudrillier, Richard L Abel, C Ross Ethier; Effects of Lamina Cribrosa Microarchitecture on Biomechanics in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4245.
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To evaluate the effects of subject-specific lamina cribrosa (LC) beam microarchitecture (orientation and connective tissue volume fraction) on optic nerve head (ONH) biomechanics. Such effects are likely important in influencing retinal ganglion cell dysfunction in glaucoma.
In this preliminary study, a porcine ONH was scanned via contrast-enhanced micro-CT (μCT); however, the approach is general and is currently being extended to human ONHs. From the scan, the 3D spatial location and orientation of LC beams were both extracted using a Frangi filter image processing technique. This LC dataset was registered against an idealized model of the ONH and posterior sclera, specifically delineating the peripapillary sclera. Fiber-informed material properties were assigned to the various tissues of this region, and the effects of elevated intraocular pressure (IOP) were simulated using computer modeling (finite element) techniques. Results were compared with a reference case in which generic material properties for the LC were used.
Compared to the reference case, inclusion of μCT-derived LC microarchitectural information reduced the computed average 1st principal strain (a measure of stretch) by 30.8% and maximum shear strain by 30.9%. Total displacement of the ONH was, on average, 4.0% lower in the fiber-informed model than in the generic model. Additionally, the strain field was more homogeneous in the fiber-informed LC than in the generic LC (Figure 1).
μCT provides a powerful tool to inject information about ONH connective tissue microarchitecture into biomechanical models of the LC. Isotropic, generic models of the LC over-estimate strain compared to anisotropic, subject-informed models, and the porous structure of the LC tends to homogenize strains within this region, reducing the presence of extreme values such that ONH axons experience minimal strain gradient.
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