Tortuous Pore Path Through the Glaucomatous Lamina Cribrosa

Abstract

The lamina cribrosa is a primary site of damage in glaucoma. While mechanical distortion is hypothesized to cause reduction of axoplasmic flow, little is known about how the pores, which contains the retinal ganglion cell axons, traverse the lamina cribrosa. We investigated lamina cribrosa pore paths in vivo to quantify differences in tortuosity of pore paths between healthy and glaucomatous eyes. We imaged 16 healthy, 23 glaucoma suspect and 48 glaucomatous eyes from 70 subjects using a swept source optical coherence tomography system. The lamina cribrosa pores were automatically segmented using a previously described segmentation algorithm. Individual pore paths were automatically tracked through the depth of the lamina cribrosa using custom software. Pore path convergence to the optic nerve center and tortuosity was quantified for each eye. We found that lamina cribrosa pore pathways traverse the lamina cribrosa closer to the optic nerve center along the depth of the lamina cribrosa regardless of disease severity or diagnostic category. In addition, pores of glaucoma eyes take a more tortuous path through the lamina cribrosa compared to those of healthy eyes, suggesting a potential mechanism for reduction of axoplasmic flow in glaucoma.

Swept-Source OCT for Evaluating the Lamina Cribrosa

“…Four articles, all by the same group, examined 3-dimensional lamina cribrosa microarchitecture changes in glaucoma using an experimental SS-OCT prototype with 5-mm axial resolution. [30][31][32][33] The poor visibility of the lamina (26%AE7% of the lamina visible on average in these studies) limits the generalizability of these findings. They examined a diverse set of measurements of the laminar pores and laminar beams using an automated segmentation algorithm.…”

“…5,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]27,28 Two other studies used a Topcon prototype OCT, 6,29 1 study used a prototype provided by Carl Zeiss Meditec (Jena, Germany), 26 and 4 studies used other unspecified experimental prototypes. [30][31][32][33] All instruments featured a scan rate of 100 000 ascans/second at wavelengths centered at 1050 nm. Axial resolution ranged from 5 to 8 mm, depending on the instrument.…”

“…These included lamina cribrosa visibility, 8,9,17,20,23,25 lamina cribrosa depth, 6,10,13,14,19,20,22 anterior laminar cribrosa insertions, 8,9,[13][14][15]18 laminar cribrosa curvature, 7,13,14,19 lamina cribrosa thickness, 17,[23][24][25] anterior lamina cribrosa defects, 5,11,12,16,21,[27][28][29] and lamina cribrosa microarchitecture. [30][31][32][33] Other studies evaluated the ability of SS-OCT to measure lamina cribrosa intensity, to image the lamina compared with SD-OCT, and to detect changes associated with glaucoma. There are no standard definitions, and acronyms have been used inconsistently in the literature.…”

Comprehensive Glaucoma Imaging

“…Another area of particular interest is the LC that is a primary site for initial glaucomatous damage. AO allows visualization of the LC microstructure and macrostructure, permitting the in-depth characterization of those structures [100][101][102][103]. LC role in glaucoma is yet to be fully understood, though AO technology paired with the deeper penetrating SS-OCT does show great promise in the ongoing study of glaucoma pathogenesis.…”

Lamina cribrosa pore movement during acute intraocular pressure rise

“…26 In another study, the LCP was found to be more tortuous in 48 glaucoma eyes as compared with healthy eyes. 27 All these studies highlighted the importance of the morphometry of the LCPs, however none of them focused on a lateral movement of the LCPs and of the lamina cribrosa.…”