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S. J. Folz, D. R. Overby; A Relationship Between Outflow Patterns and Collector Channel Ostia in Human Trabecular Meshwork. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4865.
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© ARVO (1962-2015); The Authors (2016-present)
Aqueous humor outflow is "segmental" such that only a fraction of trabecular meshwork (TM) is filtration-active at any instant, and the extent of filtration correlates with outflow resistance in bovine eyes. Factors influencing filtration patterns may thereby influence outflow resistance. In this project, we test the hypothesis that filtration patterns in human TM are influenced by the distribution of collector channel ostia.
Twelve human globes were perfused with Dulbecco’s PBS+5.5mM glucose (DBG) at 7 or 30mmHg. After baseline, anterior chambers were exchanged and perfused with DBG+fluorescent tracer microspheres (0.2µm, 0.002%), followed by perfusion fixation. Anterior segments were removed and quadrisected, and the entire TM was imaged en face with epifluorescence microscopy (10x). High and low tracer-labeled regions (2-3mm along TM) were identified and dissected for multiphoton fluorescence microscopy (47 regions, 3-4 per eye). Regions were stained with DAPI, and imaged in z-series (780nm; 200x; 20-40µm top-to-bottom) to identify collector channels and ostia based upon tissue autofluorescence and nuclei distribution. Regions were categorized as: (1) having an observable ostium; (2) having an observable collector channel, but no ostium; (3) no observable collector channel. The relative frequency of each category was analyzed statistically, comparing high and low tracer regions. Ambiguous images were excluded.
In high tracer-labeled regions, the relative frequency of categories 1, 2 and 3 were 40.3±10.4%, 19.4±7.1%, and 40.3.4±12.0% (mean±SEM; N=12), respectively. In low tracer regions, corresponding values were 0.0±0.0%, 12.5±6.5%, and 87.5±6.5%. These differences were significant for categories 1 and 3 (p=0.003 and 0.003, respectively).
Collector channel ostia were more prevalent in high tracer-labeled regions compared to low. This suggests that outflow patterns through the TM are influenced by the distribution of collector channel ostia and that ostia distribution may influence outflow resistance.Support: Supported by National Glaucoma Research, a program of the American Health Assistance Foundation (#G2006-057), and NIH (#EY018373).
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