The Effect of the Water Drinking Test on Ocular Parameters and Choroidal Thickness in Glaucoma Suspects

Abstract

Background and objectives: We aimed to evaluate the effects of the water drinking test (WDT) on several systemic and ocular parameters, including choroidal thickness, which was assessed through optical coherence tomography angiography (OCTA), in glaucoma suspects. Materials and Methods: A total of 40 eyes from 20 glaucoma suspects without any systemic or ocular diseases were included in this prospective observational study. All the participants undertook the WDT, which required the drinking of 1 L of table water in 5 min. The outcome measures included IOP, systolic and diastolic blood pressure (SBP and DBP), mean arterial pressure (MAP), mean ocular perfusion pressure (MOPP), ocular pulse amplitude (OPA), and subfoveal and peripapillary choroidal thickness, which were assessed at baseline and at four 15 min intervals after the WDT. Generalized least squares models and mixed model analyses that take into account repeated measurements were used to assess the changes over time of these parameters. Results: All the ocular and systemic parameters showed statistically significant changes at all time points compared to baseline apart from choroidal thickness. The peak changes were an IOP of 20.1 mmHg versus 17.3 mmHg at 45 min, an SBP of 137.6 mmHg versus 125 mmHg at 30 min, a DBP of 95.9 mmHg versus 85.7 mmHg at 15 min, and an MOP of 53.51 mmHg versus 48.89 mmHg at 15 min. Conclusions: Despite elevations in IOP and significant changes in all the assessed systemic parameters, the WDT was not associated with changes in choroidal thickness in glaucoma suspects.

Comparison of intraocular pressure profiles during the water drinking test and the modified diurnal tension curve

“…The similar IOP rise seen during the WDT between open-angle and closedangle patients suggests the ICA size does not play a significant role [51]. Choroidal expansion has been consistently observed following water drinking [11][12][13][14][15][16][17], however a swept-source OCT study did not show an association between IOP rise and choroidal thickness [17] which may implicate a combination of mechanisms behind the observed effect. No other major structural changes in pupil size or central corneal thickness were observed, with changes in corneal hysteresis not observed in previous work [52].…”

“…The mechanism of IOP increase during the WDT in certain individuals remains uncertain, with several hypotheses presented. Choroidal expansion during the WDT has been observed in multiple studies in both glaucomatous [ 11 – 13 ] and non-glaucomatous [ 14 – 17 ] eyes. Reduction in aqueous outflow due to increased episcleral venous pressure [ 18 ] has also been considered.…”