Purpose
To evaluate the correlation and agreement between IOP peaks and IOP fluctuations obtained with the diurnal tension curve (DTC), the water-drinking test (WDT) and the postural-change test (PCT) in glaucoma patients.
Methods
Subjects with medically treated primary open-angle glaucoma underwent DTC, WDT and PCT. Patients were hospitalized for 24 hours. During the DTC, IOP measurements were recorded with a Goldmann applanation tonometer every 3 hours in the sitting position during daytime (9 AM to 9 PM) and in the supine position with a Perkins tonometer during the nocturnal period (12PM to 6 AM). During the WDT, patients were asked to drink 1 L of water in 5 minutes, and IOP measurements were taken every 15 minutes for 1 hour thereafter. The WDT was performed after the last DTC measurement. In the PCT, IOP was measured in the seated position, and 30 minutes after the patient remained in the supine position. Only the right eye was selected for analysis.
Results
18 glaucoma patients (mean age=70.5 ± 6.8 years, mean MD = -6.1 ± 4.8 dB) were included in the study. Mean DTC IOP peak (18.72 ± 4.3 mmHg) was not statistically different from that measured by WDT (19 ± 4.56 mmHg, P=0.79) but differed from PCT (14.11 ± 3.41 mmHg, P<0.001). Mean IOP fluctuation measured during the DTC (7 ± 2.54 mmHg) was not significantly different from that measured by WDT (5.11 ± 2.76 mm Hg, P=0.06), but was higher than that obtained with the PCT (0.61±1.72 mmHg, P<0.001). The peak IOP in the diurnal curve was outside office hours in 50% (n=9) of subjects. There was a strong positive correlation between the DTC peak and the WDT peak (R=0.493, P=0.03) and a very strong positive correlation between the DTC peak and the PCT peak (R=0.722, P<0.001). However, Bland-Altman plots demonstrated poor agreement between the IOP peak measurements obtained with the 3 methods (Figures 1 and 2). We observed poor correlations between DTC and WDT fluctuations and DTC and PCT fluctuations (R=-0.125, P=0.619; R=0.349, P=0.155, respectively). Bland-Altman plots showed poor agreement between IOP fluctuations measured by the 3 tests.
Conclusions
Despite good correlation between DTC and WDT IOP peaks and DTC and PCT IOP peaks, agreement was generally poor, suggesting that the utility of these tests in estimating IOP peaks during the day may be questionable.