Water-drinking test in patients with primary open-angle glaucoma while treated with different topical medications.

OBJECTIVE: Reduction and diurnal stabilization of the intra-ocular pressure (IOP) is the mainstay of treatment for glaucoma. Fluctuations of IOP in glaucomatous patients can also be induced by the osmotic variations caused by water ingestion. Such influence can be studied by means of the water-drinking test (WDT). The aim of this study was to perform the WDT in patients with primary open-angle glaucoma (POAG) while they were being treated with different IOP-lowering medications, to test the effect of drugs with different mechanisms of action on the ability to maintain a stable IOP. METHODS: A total of 280 POAG patients were enrolled, 40 patients per group for each of the tested medications (timolol, dorzolamide, brinzolamide, travoprost,latanoprost, bimatoprost, and brimonidine). After baseline IOP measurement, all patients underwent WDT (1000 mL of water in 10 min). The IOP was measured at 15-min intervals until the return of IOP to baseline values. The main outcomes measured were mean IOP peak, mean IOP percentage increase, and mean time for returning to baseline IOP value. RESULTS: The highest mean IOP peak was found with timolol, whereas no difference was found among the other drugs. The highest mean IOP percentage increase was found with timolol, whereas bimatoprost showed an IOP percentage increase significantly lower than latanoprost, dorzolamide, and brinzolamide. The duration of IOP increase was shortest for bimatoprost and longest for timolol. CONCLUSION: This study suggests that topical medications that enhance outflow (e.g., bimatoprost, latanoprost, travoprost, and brimonidine) may provide, under stressful conditions such as the WDT, better IOP stabilization than medications that decrease aqueous humor inflow, such as timolol and topical carbonic anhydrase inhibitors.