Effect of intraocular pressure on uveoscleral outflow following cyclodialysis in the monkey eye.

Cyclodialysis was performed in both eyes of five cynomolgus monkeys. Two days later the intraocular pressure (IOP) had fallen from 17.7 +/- 0.8 to 7.1 +/- 1.4 mm Hg (P less than 0.001). At that time, both eyes were perfused for 30 min with fluorescein-isothiocyanate (FITC) dextran (MW 70,000), one at 35 mm Hg and the other at 4 mm Hg. Four pairs of control eyes (without cyclodialysis) were perfused in the same manner. At 4 mm Hg, uveoscleral outflow was 0.02 +/- 0.02 microliter/min in control eyes and 0.05 +/- 0.04 microliter/min in eyes following cyclodialysis. However, at 35 mm Hg, uveoscleral outflow in eyes with cyclodialysis increased to 2.13 +/- 0.47 microliters/min compared to 0.32 +/- 0.10 microliter/min in control eyes. Thus the "facility" of uveoscleral outflow in control eyes is 0.01 microliter/min/mm Hg and in eyes following cyclodialysis is 0.07 microliter/min/mm Hg. It is concluded that cyclodialysis results in a pressure-dependent increase in uveoscleral outflow.