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J. Grimm, J. Reynaud, H. Yang, J. C. Downs, C. F. Burgoyne; 3D Quantification of Lamina Cribrosa Microarchitecture in Normal and Early Glaucomatous Monkey Eyes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3295.
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© ARVO (1962-2015); The Authors (2016-present)
To calculate and compare lamina cribrosa beam thickness (BT) and connective tissue volume fraction (CTVF) from high-resolution, digital 3D optic nerve head (ONH) reconstructions of the normal (N) and early glaucoma (EG) eyes of 3 monkeys.
Each 3D ONH reconstruction [IOVS, 2004; 45:4378] was 3D-aligned to a confocal scanning laser tomographic (CSLT) image and the lamina cribrosa was 3D segmented [IEEE Trans Med Imag, 2006; 25:245], then skeletonized to the central spline of voxels in each beam. Laminar BT was determined at each skeletal voxel as the diameter of the largest sphere that fit inside the beam at that location. Laminar CTVF is the ratio of laminar connective tissue volume to total tissue volume in each regional sample. BT and CRVF data were mapped to a cylindrical coordinate system such that each scleral canal is a cylinder of radius 1, which allows direct regional comparisons between eyes with varying laminar/scleral geometries. Continuous 2D plots of averaged lamina cribrosa BT and CTVF were mapped to the anterior laminar surface of each eye. For each monkey, 2D laminar BT and CTVF difference maps were generated by converting the OS data to OD configuration and subtracting N from EG eye data.
Among the 3 N eyes, neither CTVF nor BT data demonstrate consistent regional distributions. Both BT and CTVF change in EG compared to N controls, with the greatest increases occurring peripherally. Glaucomatous changes in CTVF were mostly supero-temporal and/or infero-nasal, but there was no consistent pattern of change for BT.
Clinically-oriented, laminar BT and CTVF maps suggest predominantly peripheral increases in laminar BT and CTVF at the onset of CSLT-detected ONH surface change in EG. These data suggest new connective tissue synthesis in the context of remodeling and/or repair is present early in the neuropathy. For all 3 EG monkeys, regions of low CTVF in the N eye predict regions of contralateral EG eye laminar deformation and prelaminar neural tissue thickening (see abstract by H. Yang, et al).
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