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Vincent Libertiaux, Rafael Grytz, Juan Reynaud, Claude F. Burgoyne, Christopher A. Girkin, J Crawford C. Downs; Laminar Beam Orientation Surrounding Acquired Pits of the Optic Nerve (APON) in Three-dimensionally (3D) Reconstructed Human Donor Eyes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2833.
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© ARVO (1962-2015); The Authors (2016-present)
To quantify the density and orientation of laminar beams surrounding APON defects in human donor eyes.
High-resolution, 3D reconstructions of the optic nerve head (ONH) were generated for four human eyes from three donors with records-confirmed APON. The laminar microarchitecture was segmented [IEEE Trans Med Imag, 25(3):245-255, 2006] and characterized by (a) connective tissue volume fraction (CTVF), and (b) fabric tensor, a measure of predominant beam orientation and structural anisotropy [IOVS, 50(2):681-690, 2009]. The laminar microarchitecture surrounding each APON was analyzed for changes in CTVF and laminar beam direction (calculated from the fabric tensor).
While the laminar beams generally insert radially into the neural canal wall in normal eyes, the laminar beams were oriented tangent to the APON border in three of four APON eyes (Figure). In the fourth eye, which appears to be at an earlier stage of APON development due to the presence of unresorbed remnants of connective tissues in the APON region itself, the beams were only partially reoriented tangent to the pit border. CTVF did not appear changed at the APON borders.
These results suggest that the laminar microarchitecture remodels at the APON borders such that the laminar beams are predominantly oriented tangent to the pit border, although this could be an eye and/or APON specific phenomenon. Such remodeling should act to reinforce the APON edges against excessive biomechanical strain that results from the mechanical stress concentrations that form around areas in which the load-bearing connective tissues have been lost.
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