Choroidal Thickness Change after Water Drinking Is Greater in Angle Closure than in Open Angle Eyes

PURPOSE: To study change in choroidal thickness (CT) after water drinking test (WDT), comparing angle closure (AC) to open angle (OA) eyes. METHODS: Before and 30 minutes after drinking 1 L of water, 88 glaucoma subjects underwent measurements of CT by spectral domain-optical coherence tomography, IOP, blood pressure (BP), axial length (AL), and anterior chamber depth (ACD). RESULTS: Baseline CT was significantly greater in AC than in OA eyes (P = 0.002). After WDT, BP, IOP, and AL increased significantly (all P ≤ 0.0001). Mean CT increased significantly in the AC group (5.6 μm, P = 0.04, n = 40) and among 80 subjects whose IOP rose > 2 mm Hg (responders; 3.2 μm, P = 0.048), but not in the OA group or among all subjects (2.5 μm increase overall, <1% of baseline CT, P = 0.10). ACD decreased in AC (-18 μm, P = 0.07), but not in OA eyes (+3 μm, P = 0.74). AC eyes had a significantly greater IOP increase after WDT than OA eyes (P = 0.002, multivariate regression). Among responders, CT increased more in those with larger diastolic perfusion pressure increase and in AC compared to OA eyes (P = 0.04 and P = 0.053, respectively, multivariate regression). CONCLUSIONS: A significant increase in CT and a decrease in ACD after WDT were observed in AC but not in OA eyes, and IOP increased significantly more in AC than in OA eyes, suggesting that the dynamic behavior of the choroid may play a role in the AC process. IOP increase after the WDT was not fully explained by CT increase.