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C. R. Hann, D. H. Johnson; Trabecular Meshwork Pigmentation and Collector Channels - Areas of Higher Flow?. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2053.
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To determine if fluid flow is increased in proximity to collector channels in regions of heavy, medium and unpigmented trabecular meshwork.
Four pairs of whole human eyes were perfused for 30 minutes with DMEM media and then received an anterior chamber exchange with 0.5 µm FITC beads. Eyes were then perfused for 30 minutes before fixation. Two quadrants from each eye, 180° apart were analyzed. In each quadrant, 3 regions - one of heavy pigmentation, one of medium and one of unpigmented meshwork were dissected by sagittal cuts until a collector channel was found in each region. Wedges were then stained with DAPI and DiI, and serial sections examined with a Zeiss Confocal Laser Microscope. Tissue volumes ranged from 15-20 µm. The amount of beads in each region was determined by measuring the area of fluorescence. To determine the effect of pressure on bead distribution, two pairs were perfused at 10 mm Hg and two pairs at 25 mm Hg.
In eyes perfused at 25 mmHg regions of heavy pigmentation had more beads than unpigmented regions (4.9±3.5% vs. 1.1±0.9% of trabecular meshwork area, p=0.02). Beads were more common underlying collector channels than regions farther away in the same section. Perfusion at higher pressure (25 mmHg) resulted in 3 times the amount of fluorescence at the collector channel than in perfusion at lower pressures (10 mmHg) in regions of heavy and medium pigmentation. Morphologic examination revealed focal areas of herniations of Schlemm’s canal cells into the canal lumen in areas underlying collector channels in one third of specimens examined. Although beads were present near these herniations they were not concentrated in the herniations.
Fluid flow is increased in trabecular meshwork regions containing heavy pigmentation and collector channels.
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