Correlation and agreement between the 24-hour diurnal tension curve, the water-drinking test, and the postural-change test in glaucoma patients

Abstract

Aim: To investigate whether the water-drinking test (WDT) and the postural-change test (PCT) can predict the 24-hour diurnal tensional curve (DTC) intraocular pressure (IOP) peak and fluctuation by assessing the correlation and agreement between these three tests in medically treated primary open-angle glaucoma (POAG) patients.Methods: 18 POAG patients underwent the DTC, WDT and PCT. Pearson’s correlation coefficient and Bland-Altman plots were used to assess the correlation and agreement between the results, respectively.Results: Mean DTC IOP peak was 18.72 + 4.31 mmHg and mean DTC IOP fluctuation was 7.00 + 2.54 mmHg. The IOP peak was outside office hours in 50% of the subjects. We observed poor correlations between the DTC and WDT fluctuations and the DTC and PCT fluctuations (r=-0.125, P=0.619; r=0.349, P=0.155, respectively). There was a moderate positive correlation between the DTC and WDT peaks (r=0.493, P=0.03) and a strong positive correlation between the DTC and PCT peaks (r=0.722, P<0.001). However, Bland-Altman plots demonstrated poor agreement between the IOP peaks and fluctuations between the 3 tests. WDT and DTC IOP peaks differed by 2 mmHg or more in 56% of the measurements. PCT and DTC IOP peaks showed that 83% of the measurements had differences greater than 2 mmHg.Conclusions: Despite moderate to strong correlations between DCT and WDT peaks and DTC and PCT IOP peaks, the agreement was generally poor, suggesting that they should be used with caution to estimate peak IOP.