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Hongli Yang, Howard Lockwood, Juan Reynaud, Lirong Qin, Galen Williams, Stuart Keith Gardiner, Claude F Burgoyne; Global Lamina Cribrosa Microarchitectural Change in Monkey Experimental Glaucoma (EG) from Early through Advanced Axon Loss. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© 2017 Association for Research in Vision and Ophthalmology.
To quantify the global distribution of laminar beam diameter (BD) and pore diameter (PD) in 6 bilateral normal and 24 unilateral EG animals sacrificed at early (n=14, 0-35%) through advanced (n=10, 58-85%) EG eye axon loss.
Each optic nerve head (ONH) underwent digital 3D reconstruction and lamina beam segmentation.1,2 Total axons were counted in each optic nerve.3 Within each ONH, each beam and pore voxel was assigned a diameter based on the largest sphere that contained it.1 The distributions of BD and PD for voxels within each ONH were fit to a gamma distribution, which can be summarized by two parameters: scale and shape. The estimated mean of the distribution is given by scale*shape. EG vs control eye differences in ‘scale’ suggest that all sizes changed by the same proportion. Differences in ‘shape’ indicate that some sizes changed by a greater proportion than others. For each animal, the % inter-eye differences in each parameter were calculated, and these were compared to zero using t-tests.
In early axon loss, while BD parameters were unchanged, the scale and estimated mean of the PD distribution were significantly larger in EG compared to control eyes (p=0.020 and p=0.003, respectively) (Table). Because the shape of the PD distribution was not significantly different (p=0.533), early PD expansion appeared to be uniform among pores of all diameters. In advanced axon loss, EG eye BD distribution shape (p=0.019) and estimated mean (p=0.003) were significantly decreased. EG eye PD distribution shape was further decreased (p=0.008), scale was increased (p=0.008) and estimated mean was increased (p=0.031) but not beyond the value at early axon loss.
Global pore diameter increases without significant changes in global beam diameter through early axon loss in monkey EG. In advanced axonal loss, pore diameters remain enlarged and beam diameters decrease with both phenomena being non-uniform across beams and pores of different sizes. The mechanisms that link laminar deformation and remodeling and laminar microarchitectural change to early and late axonal insult are currently under study.1Lockwood H, et al. IOVS 2015; 56 (3):1618-372Grau V, et al. IEEE Trans Med Imaging 2006; 25:245-2553 Reynaud J, et al. IOVS 2012; 53:2951-2959.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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