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W. D. Hu, F. A. Medeiros, L. M. Alencar, J. H. Liu, R. Susanna, R. N. Weinreb; The Correlation Between the Water Drinking Test and 24-Hour Intraocular Pressure Measurements in Glaucomatous Eyes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1272.
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The water-drinking test (WDT) has been proposed as a simple test to evaluate intraocular pressure variations in glaucomatous patients. The purpose of this study was to determine if the IOP rise measured during the WDT was related to the peak intraocular pressure or IOP fluctuations measured during the 24-hour period in patients with primary open angle glaucoma (POAG) being treated with different ocular hypotensive medications.
Eleven POAG patients using ocular hypotensive medications (latanoprost or combination therapy of latanoprost and timolol, or latanoprost and brinzolamide) underwent the WDT after at least 8 weeks of treatment. Two of the patients repeated the test 8 weeks after changing medications, for a total of 26 tests. After baseline IOP measurement, all patients underwent WDT by drinking 1000 mL of bottled water in 5 minutes. The IOP was measured at 15, 30, 45, 60, 90, and 120 minutes after ingestion of the water. We reviewed the charts of 24-hour IOP data obtained from these patients. Within a week of the WDT, patients were housed for 24 hours in a sleep laboratory. Intraocular pressure was measured every 2 hours using a pneumatonometer in the sitting and supine positions during the 16-hour diurnal/wake period and in the supine position during the 8-hour nocturnal/sleep period. The main outcomes measured were the mean IOP peaks for the WDT and 24-h IOP curve, the correlation between the WDT and 24-h IOP peaks, and the correlation between the WDT and 24-h IOP fluctuations. Bland and Altman plots were used to evaluate the agreement between 24-h IOP peak, WDT, and office IOP measurements. Generalized estimated equations were used to adjust for the correlations between measurements obtained on the same individual.
The mean IOP peak for the WDT was 19.9 ± 4.0 mmHg whereas the mean IOP peak for the 24-hour IOP measurements was 22.4 ± 3.5 mmHg. The IOP peaks for the WDT and 24-hour IOP measurements were significantly correlated (r=0.843, P<0.001). The IOP fluctuation during the WDT was not significantly correlated to the IOP fluctuation observed at the sleep lab (r=0.228, P=0.396). The agreement between WDT peak IOP and 24-h peak IOP was better than the agreement between any of the isolated IOP measurements obtained during office hours and 24-h peak IOP.
The peak IOP measured during the WDT was strongly correlated to the peak IOP obtained during the 24-h period. Although the WDT tended to underestimate the 24-h peak IOP in some patients, its ability to predict the 24-h peak IOP was superior to that of IOP measurements obtained during office hours.
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