Preferential fluid flow in the human trabecular meshwork near collector channels

To determine whether preferential pathways exist within the human trabecular meshwork, pigmented and nonpigmented regions adjacent to and between collector channels were examined, and the configuration of the juxtacanalicular tissue (JCT) was analyzed.

Healthy whole human eyes were perfused at 10 or 25 mm Hg with 0.5 mum fluorescent beads. Tissue wedges of pigmented and nonpigmented meshwork (with and without collector channels) were dissected from each eye and examined by confocal microscopy. Bead concentration adjacent to and between collector channels was quantified. The configuration of the JCT adjacent to collector channels from whole eyes perfused at 20 mm Hg was analyzed by light microscopy.

Eyes perfused at 25 mm Hg had more beads adjacent to collector channels in pigmented than in nonpigmented regions (4.9%+/-3.5% vs. 1.1%+/-0.9%; P=0.02). In pigmented regions without collector channels, bead concentration was decreased by fivefold (4.9%+/-3.5% vs. 0.96%+/-0.88%; P=0.04). Perfusion at 25 mm Hg increased beads by threefold under pigmented collector channels compared with the same regions in eyes perfused at 10 mm Hg. Expansion of the JCT occurred more often under collector channels at 25 mm Hg than at 10 mm Hg (44% vs. 17%; P=0.01). The JCT region under collector channels was expanded compared with JCT regions between adjacent collector channels (1053+/-424 microm(2) vs. 571+/-216 microm(2); P<0.001).

Increased levels of beads in pigmented trabecular meshwork adjacent to collector channels suggest preferential flow pathways are present in human trabecular meshwork. At elevated pressure, the JCT region under collector channels is expanded, possibly because of increased fluid flow.