Characterization of uveoscleral outflow in enucleated porcine eyes perfused under constant pressure

PURPOSE. A new technique was developed to measure the flow of aqueous humor through the uveoscleral pathway in porcine eyes and to examine whether there is any outflow through the choroid into the vortex veins. METHODS. Enucleated porcine eyes were perfused in vitro under a constant pressure of 10 mm Hg. After total outflow was measured, the episcleral vessels were blocked with cyanoacrylate to eliminate outflow through the conventional pathway. The vortex veins were then blocked, to assess the amount of choroidal drainage. RESULTS. The average outflow in control eyes was found to be 2.8 ± 0.9 μL/min. After the exit sites of the conventional pathway were blocked, the average outflow decreased to 1.1 ± 0.5 μL/min. Blocking the vortex veins did not appear to alter uveoscleral outflow further (1.2 ± 0.8 μL/min). CONCLUSIONS. The results suggest that choroidal drainage into the vortex veins is insignificant in the absence of blood perfusion. No significant washout effects in porcine eyes were observed.