Purpose:
The supination and water drinking tests (WDT) transiently increase intraocular pressure (IOP). The goal of the study is to determine the relationship between these two tests.
Methods:
Twenty-two prospectively recruited patients were included in the study. For each patient, IOP was recorded in both eyes at different time intervals, and the peak IOP was used for analysis. First, a supination test was performed. Following a baseline IOP measurement, IOP measurements were taken at 1 and 5 minutes after supination. Following a second baseline IOP measurement, a WDT was performed. Patients consumed 800cc of water over 5 minutes and IOP measurements were taken at 15 and 30 minutes following water consumption.
Results:
IOP measurements during the supination test and the WDT were well correlated (r=0.831, p<0.001). However, Bland-Altman plots revealed remarkable discrepancy between these two variables in a large proportion of patients. (Fig. 1). The difference between IOP measurements obtained by the two tests was 2 mmHg or more in 46% of patients, with 55% of these patients demonstrating higher IOP measurements with the supination test than the WDT. In addition, when comparing the two tests, the absolute change in IOP from baseline and the percent change in IOP from baseline were not correlated (r=0.0903, p=0.689 and r=0.0933, p=00.679, respectively).
Conclusions:
Although the IOP measurements from the supination and water drinking tests were well correlated, they had poor statistical agreement. In addition, the absolute and percentage increase from baseline between these two tests were not well correlated. Our findings show that the supination and water drinking tests are not equivalent.Figure 1. Bland-Altman plot showing poor statistical agreement in IOP measurements between the supination and water drinking tests.
Keywords: intraocular pressure • clinical (human) or epidemiologic studies: systems/equipment/techniques