In-Vivo 3D Lamina Cribrosa Microstructure Characterization of Healthy Non-Human Primates

Abstract

Purpose : Non-human primate (NHP) optic nerve head (ONH) has been commonly utilized in the study of glaucoma pathogenesis. To set the foundation for future LC studies, we aim to characterize the in-vivo 3D structure of healthy NHP’s LC.

Methods : In-vivo ONH spectral-domain OCT scans (Leica, Chicago, IL) were obtained from healthy adult anesthetized Rhesus Macaques. Using a previously described semi-automated segmentation algorithm, microstructure measurements were obtained using ImageJ. The LC measurements were assessed in central and peripheral regions of an equal area, in quadrants and depth-wise. The nasal quadrant was excluded from the analysis due to poor LC visibility (calculated as a ratio between visible LC and optic disc areas). Linear mixed-effects models were used to compare parameters among regions, adjusting for visibility, age, analyzable depth, scan quality, disc area, and the correlation between eyes.

Results : 16 eyes of 10 animals (7 males, 3 females; 9 OD, 7 OS) were available for analysis with a mean age of 10.5 ± 2.1 years. The mean analyzable depth was 175 ± 37 µm, with average LC visibility of 25.4 ± 13.0 % and average disc area of 2.67±0.45 mm². The central region showed statistically significantly thicker beams than the periphery (Table). Quadrant based analysis showed smaller mean pore area and larger beam-to-pore ratio in the superior quadrant compared to the inferior. The beams and pores of the middle third of the lamina depth were significantly larger than the anterior third.

Conclusions : In-vivo OCT analysis of the healthy NHP showed significant regional variations in their LC microstructure. The central area consisted of wider beams, presumably to support thicker central nerve bundles. The middle LC had larger beams and pores than the anterior, which might reflect the merging of bundles to form the optic nerve. These findings offer anatomic context captured in-vivo with OCT to future experimental glaucoma models, especially when considering localized LC changes.

This is a 2020 Imaging in the Eye Conference abstract.