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Karun S. Arora, Joan L. Jefferys, Eugenio A. Maul, Harry A. Quigley; Choroidal Thickness Increase Is Different among Angle-Closure Versus Open-Angle Eyes but Does Not Explain IOP Rise after Water Drinking. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4173.
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1) To measure potential change in choroidal thickness (CT) as a cause of intraocular pressure (IOP) rise during the water-drinking test (WDT); 2) To compare WDT responses in persons with open angle glaucoma (OAG), OAG suspects (OAGS), angle closure (AC), AC suspects (ACS) and AC glaucoma (ACG).
Spectral domain optical coherence tomography scans of the macula with enhanced depth imaging were obtained (one eye per subject) before and 30 minutes after drinking 1 liter of water, in 25 ACS/AC/ACG and 48 OAGS/OAG subjects. Standard demographics, degree of field loss, and blood pressure were measured (before and after WDT). Average CT (6 mm scan centered on fovea) was measured with Image J software, and univariable and multivariable statistics were performed.
Baseline CT was thicker in ACG than OAG eyes (312 vs. 244µm, p=0.03). However, CT has been shown to be inversely related to axial length (AL), and OAG eyes had longer AL than ACG eyes (24.3 vs. 23.0 mm, p<0.0001), possibly accounting for this difference. After WD, mean IOP rose 40% (5.51 + 3.51 mm, p<0.0001), and systolic, mean and diastolic blood pressures (BP) also rose (8.9, 6.4, and 5.1 mm Hg, respectively, all p<0.0001), as did systolic perfusion pressure (PP, 3.4 mm Hg, p=0.01). The AL also increased (0.012 mm, p=<0.0001), though the increase was not significantly different between OA and AC eyes (0.009 mm vs. 0.017 mm, p=0.19). The observed increase in AL, most likely associated with an increase in eye volume caused by the increase in IOP, matched the expected increase in AL calculated using the pressure-volume relationship for the eye described previously (Silver and Geyer, Curr Eye Res 2000). Mean CT increased, but insignificantly (1.4 + 16.3 µm, p=0.46). Overall IOP change was not significantly associated with CT change (p=0.8). CT change was unrelated to age, sex, gender, axial length, visual field defect level, baseline IOP or baseline CT. In multivariable models in 64 eyes with >2 mm IOP rise, CT change was significantly related to change in mean or diastolic PP (p=0.02, 0.01), and AC eyes had greater change in CT than OA eyes (p=0.03).
CT is responsive to PP, yet IOP increase in WDT is associated with BP rise but not with CT increase, suggesting it results from changed aqueous in/outflow related to adrenergic stimulation. Our results confirm thicker choroid in AC eyes and differences in CT reactivity in AC versus OA eyes.
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