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Vincent Libertiaux, Massimo Antonio Fazio, Lan Wang, Brandon Smith, Christopher A Girkin, J Crawford C Downs; Regional Variations of Laminar Beam Orientation, Connective Tissue Volume Fraction and Anisotropy in Three-dimensionally Reconstructed Optic Nerve Heads (ONH) from Human Donor Eyes: A Comparison Between Normal (N) and Glaucomatous (Gl) Eyes.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4265.
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To quantify the regional variation of the density, orientation and degree of anisotropy of laminar beams in normal and glaucomatous human donor eyes and determine the significant difference between them, if any.
High-resolution, 3D reconstructions of the ONH were generated for four clinically confirmed normal and two clinically confirmed glaucomatous human donor eyes from six donors. Eyes were immersion fixed at 10 mmHg and reconstructed using a custom automated microtome-based system that serially images the embedded tissue block face at 1.5 µm resolution in the fluorescent domain after each 1.5 µm section is cut. The images are then aligned and stacked into a digital 3D ONH reconstruction with 1.5x1.5x1.5 µm voxel resolution. The lamina cribrosa (LC) architecture was delineated and segmented and the laminar microarchitecture was sampled on a discrete grid to compute the connective tissue volume fraction (CTVF), the degree of anisotropy and the predominant laminar beam orientation within each sampling volume. CTVF, LC beam orientation, and LC beam anisotropy were mapped for each eye and compared.
For the eyes quantified, the variables of interest show an eye-specific distribution with no clear trend or pattern either within each group (Gl and N) or across them. The previously reported hourglass-shaped LC beam density, with bigger pores and less connective tissue in the superior and inferior quadrants (Ar. of Opthal., 99:137-143, 1981) was not observed in any of the six eyes. (Figure)
Results suggest that CTVF, LC beam orientation and anisotropy at the periphery of the LC vary regionally in both normal and glaucomatous human eyes , which likely influence the biomechanical behavior of the LC and ONH. No consistent pattern was observed for these parameters, which contradicts previous reports.
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