Abstract
Purpose :
Though a non-uniform glycocalyx layer covers the endothelium of the trabecular outflow pathway in bovine and human eyes, the differences in glycocalyx morphology between regions of different flow types in normal and diseased eyes have not been explored. This study examined glycocalyx morphology in high- and low-flow regions in normal and laser-induced ocular hypertensive monkey eyes.
Methods :
YAG laser photocoagulation burns were created along ~270 degrees of the trabecular meshwork (TM) of one eye (n = 6) or both eyes (n = 2) of each monkey, reducing outflow in these regions, until a consistent rise in intraocular pressure was noted. Portions of the TM were not lasered, allowing outflow. Unlasered eyes (n = 6) served as controls. Monkeys were euthanized ≥60 months after the last laser treatment. Eyes were enucleated and perfused at 15 mmHg to measure outflow facility, outflow pattern was labeled with fluorescein, then eyes underwent perfusion-fixation for glycocalyx labelling. Anterior segments were cut into ~36 radial wedges and processed for electron microscopy. Coverage and thickness of the glycocalyx were measured in the TM, Schlemm’s canal (SC), collector channels (CCs), intrascleral veins (ISVs), and episcleral veins (ESVs) in non-lasered regions of laser-treated eyes and high- and low-flow regions of controls.
Results :
Median outflow facility was significantly less in laser-treated eyes compared to controls (P = 0.02). A trend of increasing glycocalyx thickness from the TM to ESVs was noted in non-lasered regions of lasered eyes and controls. No significant differences were found in glycocalyx coverage and thickness between high- and low-flow regions of controls. In non-lasered regions of lasered eyes, glycocalyx thickness was less when compared to high-flow regions in SC and CCs and low-flow regions in CCs (P < 0.05), and coverage was less when compared to high-flow regions in TM and SC and low-flow regions in SC (P < 0.05). In lasered regions of laser-treated eyes, TM, SC, and CCs were partly to completely obliterated, and ISVs and ESVs rarely showed glycocalyx labeling.
Conclusions :
Laser treatment of the TM resulted in a decrease in glycocalyx coverage and/or thickness in lasered and non-lasered regions. Whether these changes contribute to decreased outflow facility needs further investigation.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.