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Vincent Libertiaux, Massimo Antonio Fazio, Brandon Smith, Lan Wang, Christopher A Girkin, J Crawford C Downs; Regional and Sectorial Variations of Laminar Beam Orientation, Connective Tissue Volume Fraction (CTVF) and Anisotropy in 3D Reconstructed Optic Nerve Heads (ONH) from Normal Human Eyes. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6156.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the regional and sectorial variability of CTVF, beam orientation, degree of anisotropy of the lamina cribrosa (LC) in eyes from donors of European descent (ED).
High-resolution 3D reconstructions of the ONH were generated for 20 clinically confirmed normal human donor eyes immersion fixed at 10 mmHg from 10 donors (ED, mean age = 74.1 +/- 8.2 y.o). A custom, microtome-based 3D tissue reconstruction system serially images the embedded tissue block face in the fluorescent domain after each section is cut, creating a 1.5x1.5x1.5 µm digital ONH volume. The LC architecture was delineated and segmented and its microarchitecture was sampled on a grid to compute the variables of interest within each sampling volume.<br /> The data were then binned into 8 radial sectors and 2 regions based on posterior LC surface area (75% central and 25% peripheral) and linear mixed effects models were used for determining sectorial/regional differences and an ANOVA was performed for assessing intra- and inter-donor differences.
The sectorial analysis showed that the CTVF is significantly lower in the inferior sector and higher in the superotemporal sector (diff. 34.3%, p<0.001). The peripheral lamina exhibits significantly higher CTVF than the central region (p<0.001). Anisotropy, or degree of beam alignment, was significantly lower in the inferior sector and higher in the nasal sector (diff. 28.4 %, p<0.001). For all variables, the intra-donor correlation was higher than the inter-donor correlation (p < 0.001). The figure shows the sectorial and regional distribution of CTVF and anisotropy.
Results suggest that CTVF, anisotropy and the predominant beam orientation vary significantly both regionally and sectorially in human eyes from older ED donors. All variables varied significantly between regions and sectors, which likely leads to local differences in laminar and ONH biomechanical behavior. Generally, the inferior sectors showed the lowest LC connective tissue density and the superior sectors showed the highest, which does not match previous 2D studies of LC morphology. The lower CTVF in the inferior sector likely leads to higher mechanical strains, which correlates with the common patterns of damage in glaucoma.
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