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William Watkins, David Robertson, Karen Joos; Effect of the Water Drinking Test in Subjects with Pure Autonomic Failure and Normal Tension Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1984.
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Intraocular pressure (IOP) is influenced by systemic vascular control. Pure autonomic failure (PAF) patients have elevation of blood pressure (BP) and symptomatic improvement following water consumption. This study examines the effect of water consumption on BP, IOP, and central choroidal thickness (ChT) in subjects with (PAF) or normal tension glaucoma (NTG).
This study was approved by the Vanderbilt University IRB (ClinicalTrials.gov NCT00338065) and informed consent was obtained from all subjects. PAF (n=10), NTG (n=10), and control (n=10) subjects were evaluated by baseline mean arterial systemic blood pressure (MAP), Goldmann and Tono-pen (Reichert Technologies, NY) tonometry, and optical coherence tomography (OCT, Spectralis, Heidelberg, CA) central choroidal thickness (ChT). The subjects then consumed 500 ml of room-temperature water within 5 minutes. MAP, tonometry, and ChT measurements were obtained 15 minutes after water consumption. The method to obtain ChT was adapted from Mwanza, et al with the Spectralis OCT enhanced depth imaging protocol.
Baseline MAP (mm Hg) for each group was 68+14.5 (PAF), 97.7+8.2 (NTG), and 97.8+8.8(Control). After water consumption, the MAP increased to 87.1+11.2 (PAF,P<0.001), 100.7+13.5 (NTG,P=0.09), and 101.26+8.4(Control,P=0.03). Baseline IOP (mm Hg) for each group was 14.5 +3.5 (PAF), 13.4+2.9(NTG), and 16.8+1 .4(Control). After water consumption, the IOP increased to 19.5+3.0 (PAF,P< 0.001), 15.2 +3.4 (NTG,P< 0.001), and 17.4+1.4 (Control,P<0.004). The 15-minute mean IOP was greater in the PAF than the control group (P<0.001, Mann-Whitney Rank Sum Test ). Regarding ChT, the increase following water consumption in all three groups was not statistically significant. PAF subjects demonstrated the greatest change in ChT (5.1+3.4%,P=0.06) followed by NTG subjects (4.8+3.0%,P=0.18), and controls (2.7+5.0%,P=0.36).
This study demonstrated a statistically significant increase in IOP in all three subject groups with the greatest increase occurring in the PAF group. A statistically significant change in MAP was seen in both the control group as well as the PAF group following water consumption. However, no subjects demonstrated a significant change in ChT. This study provides evidence that water consumption may influence IOP as well as MAP in patients with PAF.
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