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Gustavo Rosa Gameiro, Pedro Monsalve, Vittorio Porciatti; Neuro-Vascular changes associated with the Water Drinking Stress Test. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5852.
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© ARVO (1962-2015); The Authors (2016-present)
The Water Drinking Test (WDT) is used to temporarily elevate intraocular pressure (IOP) and predict peak IOP in glaucoma to help determinate risk of progression. This study investigates unknown neurovascular changes associated with WDT in normal subjects.
Eleven healthy young subjects (mean age 32 ± 7.8 years) participated in this study. WDT typically consisted of drinking 1 liter of water within 5 minutes. Outcome measures were IOP (Reichert PT-100), mean brachial blood pressure (MAP), heart rate (HR), and steady-state pattern electroretinogram (PERG, Jorvec Corp), which were assessed before WDT and 4 times after at 15 minutes interval. The same protocol was repeated in a different session without WDT as a measure of test-retest variability. IOP and PERG measures of each eye were averaged and used as single entry in the statistical analysis. Significant changes of outcome measures over time were assessed with repeated measures ANOVA and post-hoc t-tests.
While the control recording without WDT did not show significant changes over time (p> 0.5) in all outcome measures, WDT resulted in significant peak changes of the following parameters compared to baseline: IOP: baseline 17.67 ± 2.52 mmHg, 30 min after WDT, 20.39 ± 4.13 (p<0.0001); MAP: baseline, 89.75 ± 10.08 mm Hg, 15 min after WDT, 94.15 ± 9.73 mm Hg (p=0.05); HR: baseline 69.32 ± 8.26 bpm, 15 min after WDT 59.27 ± 8.41 bpm, (p<0.0001); PERG phase: baseline 67.8 ±11.3 deg, 15 min after WDT, 59.2 ± 11.03 deg (P=0.0002). The PERG amplitude was not different (p=0.2) before (1.28 ±0.42 µV) and after WDT (1.21 ± 0.31 µV).
In addition to IOP elevation, WDT is associated with measurable changes of systemic blood pressure and retinal ganglion cell function in healthy subjects. As these represent risk factors for glaucoma, their assessment might increase the predictive power of the WDT for glaucoma development. Of note, head-down posture in control subjects also results in comparable IOP elevation and PERG phase delay (J Glaucoma 2013, 22:255-64). However, hemodynamic changes (MAP) upon head-down posture and after WDT occur in opposite directions.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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