Role of the water-drinking test in medically treated primary open angle glaucoma patients.

PURPOSE: The water-drinking test (WDT) has recently re-emerged as a possible way to determine the competency of the trabecular meshwork. We performed a prospective interventional study to test the hypothesis that the WDT could be useful in assessing fluctuations in patients undergoing treatment for primary open angle glaucoma (POAG).

METHODS: We included 122 patients; 62 on medical treatment for POAG (n=123 eyes) and 60 controls (n=120 eyes). The study group had been on intraocular pressures (IOP) lowering treatment continuously for at least 3months with stable IOP. The WDT was performed during fasting and was considered positive if it fluctuated ≥6mmHg.

RESULTS: The patients on medical treatment had a mean age of 50.56±18.45 years vs. 51.35±11.22 for the controls (P=0.34); with 71% being female in the study group and 77% in the control group. In the study group; 52% were on beta blockers (n=64), 27% combination of two or more medications (n=33), 19% prostaglandin analogues (n=24) and 2% alpha agonists (n=2). The WDT was positive in 17.07% (n=21) in the study group and 2.5% (n=3) in the control group (P=0.0001). The mean fluctuation was 7.14±2.15mmHg in the study group and 6.00±0mmHg in the controls (P=0.33). A positive WDT was found in 33.33% (n=11) of those on combination therapy; 12.5% (n=3) prostaglandin analogues and 10.94% (n=7) beta blockers (P=0.03). Combination therapy had the highest positive WDT fluctuation (7.54±2.87) followed by prostaglandin analogues (7.00±1.00) and beta blockers (6.57±0.78) with a P value of 0.44.

CONCLUSIONS: The WDT can identify significant fluctuations in eyes with POAG that are medically treated.