The Relationship Between Choroidal Expansion and Intraocular Pressure Rise During the Water Drinking Test in Healthy Subjects and Patients With Exfoliation Syndrome

To evaluate the changes in choroidal thickness (ChT) and intraocular pressure (IOP) during the water drinking test (WDT) in patients with exfoliation syndrome (XFS).In this prospective study, 20 eyes of 20 patients with XFS and 20 eyes of 20 healthy subjects underwent measurements of subfoveal ChT, IOP, systolic and diastolic blood pressure before and 30 and 60 minutes after the WDT. WDT involved ingestion of 1 L of water within 5 minutes. χ test and analysis of variance were used for the statistical analysis.There were no significant differences between the 2 groups with respect to age (P = 0.238), sex (P = 1.000), central corneal thickness (P = 0.714), axial length (P = 1.000), diastolic blood pressure (P = 0.350), systolic blood pressure (P = 0.064), and IOP (P = 0.234) before water ingestion. Baseline ChT was lower in the XFS group (285.1 ± 69.1 μm) as compared with that of controls (339.4 ± 81.2 μm) (P = 0.028). ChT was found to be significantly increased at 30 and 60 minutes after water ingestion in the XFS group (P < 0.001), whereas in the control group an increase was found only at the 60-minute time-point (P = 0.028). Independent of baseline ChT, at 60-minute endpoint, the magnitude of choroidal expansion was higher in XFS eyes (13.2 ± 14.3%) compared with control eyes (6.2 ± 3.5%) (P = 0.028). The mean IOP was higher at all time-points with respect to their respective baseline values in both XFS (P = 0.002, P < 0.001) and control (P = 0.038, P = 0.002) eyes.Choroidal expansion during WDT does not seem to be an important mechanism for IOP elevation in healthy eyes or those with XFS. Furthermore, the similarity of IOP increase to controls suggests that trabecular outflow facility is not impaired in eyes with XFS.