Differences in Outflow Facility between Angiographically Identified Highversus Low-flow Regions of the Conventional Outflow Pathways in Porcine Eyes

PURPOSE. To investigate differences in outflow facility between angiographically deter-mined high-and low-flow segments of the conventional outflow pathway in porcine eyes. METHODS. Porcine anterior segments (n = 14) were mounted in a perfusion chamber and perfused using Dulbecco's phosphate buffered solution with glucose. Fluorescein angiography was performed to determine high-and low-flow regions of the conventional outflow pathways. The trabecular meshwork (TM) was occluded using cyanoacrylate glue, except for residual 5-mm TM areas that were either high or low flow at baseline, designating these eyes as "residual high-flow" or "residual low-flow" eyes. Subsequently, outflow was quantitatively reassessed and compared between residual high-flow and residual low-flow eyes followed by indocyanine green angiography. RESULTS. Fluorescein aqueous angiography demonstrated high-flow and low-flow regions. Baseline outflow facilities were 0.320 +/- 0.08 and 0.328 +/- 0.10 !IL/min/mmHg (P = 0.676) in residual high-flow and residual low-flow eyes before TM occlusion, respec-tively. After partial trabecular meshwork occlusion, outflow facility decreased to 0.209 +/- 0.07 !IL/min/mmHg (-32.66% +/- 19.53%) and 0.114 +/- 0.08 !IL/min/mmHg (-66.57% +/- 23.08%) in residual high-and low-flow eyes (P = 0.035), respectively. There was a significant difference in the resulting IOP increase (P = 0.034). CONCLUSIONS. Angiographically determined high-and low-flow regions in the conven-tional outflow pathways differ in their segmental outflow facility; thus, there is an uneven distribution of local outflow facility across different parts of the TM.