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Vincent Libertiaux, Rafael Grytz, Juan Reynaud, Christopher Girkin, J Crawford Downs; Laminar Beam Orientation and Connective Tissue Volume Fraction in Three-dimensionally (3D) Reconstructed Optic Nerve Heads (ONH) from Human Donor Eyes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):58.
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© ARVO (1962-2015); The Authors (2016-present)
To quantify the density and orientation of laminar beams in normal human donor eyes.
High-resolution, 3D reconstructions of the ONH were generated for three normal human donor eyes immersion fixed at 10 mmHg using a custom, microtome-based 3D tissue reconstruction 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 (Grau et al., IEEE TMI 2006; Downs et al, IOVS 2007) and the laminar microarchitecture was sampled on a discrete grid to compute the connective tissue volume fraction (CTVF) and the predominant laminar beam orientation within each sampling volume (Roberts et al, IOVS 2009). The use of overlapping sampling volumes allowed the generation of a smooth, continuous CTVF and beam orientation maps.
For the eyes processed, the laminar beams are generally oriented radially in the periphery of the LC in the inferior-nasal (IN) sector and tangentially aligned in the superior-temporal (ST) quadrant (Figure). The IN region systematically presented the highest degree of beam orientation anisotropy. In these three volumes, no consistent CTVF pattern seemed to emerge.
Results suggest that CTVF and the fiber orientation at the periphery of the LC vary regionally in human eyes, which likely influence the biomechanical behavior of the LC and ONH.
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