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CB Toris, G-L Zhan, CB Camras, MA McLaughlin; Travoprost Increases Uveoscleral Outflow in Monkeys . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1970.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the mechanism by which travoprost, a prodrug of a prostaglandin F2α analog, reduces intraocular pressure (IOP) in cynomolgus monkey eyes. Methods: One eye each of 12 monkeys was treated with laser burns to the trabecular meshwork to elevate IOP. At least two months later (Baseline Day), IOP was measured by pneumatonometry (9:00 and 12:00), and aqueous flow and outflow facility were determined by a fluorophotometric method. Uveoscleral outflow was calculated. Two months later, both eyes were treated with travoprost 0.004% at 9:00 and 17:00 for two days and at 9:30 on the third day (Treatment Day), when measurements were repeated as on Baseline Day. Statistical analyses were done using two-tailed, paired t-tests. Results: Compared to normotensive eyes, hypertensive eyes on Baseline Day had higher IOP (33.5±13.4 mean±SD vs 22.8±3.7 mmHg; p=.03), and lower outflow facility (0.07±0.06 vs 0.15±0.07 µl/min/mmHg; p=.04). In the hypertensive eyes on Treatment Day vs Baseline Day, IOP was reduced at 2.5 (25.8±11.2 vs 33.5±13.4 mmHg; p=.02) and 16 hours (26.3±10.2 vs 35.4±13.2 mmHg; p=.02) after treatment. Uveoscleral outflow was increased (1.1±0.9 vs 0.7±0.9 µl/min) but this was not significant (p=.3). In the normotensive eyes on Treatment Day vs Baseline Day, IOP was reduced at 2.5 (19.0±3.7 vs 22.8±3.7 mmHg; p=.04) but not at 16 hours after treatment, and uveoscleral outflow was increased (1.0±0.4 vs 0.4±0.7 µl/min; p=.02). No other parameters were significantly altered by treatment. Conclusion: Travoprost reduces IOP in normotensive monkey eyes by increasing uveoscleral outflow. The IOP reduction in hypertensive eyes is probably via the same mechanism, although the increased drainage did not reach statistical significance due to large standard deviations. Consistent with published results for other prostaglandin analogs, aqueous flow and outflow facility were not altered by travoprost.
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