Comparison of the Intraocular Pressure Variation Provoked by Postural Change and by the Water Drinking Test in Primary Open-angle Glaucoma and Normal Patients

Purpose:To evaluate the intraocular pressure (IOP) peak and variability detected by moving the body from sitting to supine position (postural test) and by the water drinking test (WDT) in normal and primary open-angle glaucoma (POAG) subjects.Patients and Methods:Prospective, cross-sectional observational analysis of 14 eyes of 14 normal subjects and 31 eyes of 31 patients with POAG. All POAG subjects were under clinical therapy. IOP measurements were all performed on the same day.Results:When the subjects moved to the supine position, there was an IOP increase of 1.361.34 and 2.84 +/- 2.21 mm Hg in the normal and POAG groups, respectively (P=0.011). During the WDT, mean IOP peak and fluctuation in the POAG group was 19.29 +/- 4.10 and 4.13 +/- 2.33 mm Hg, respectively. These levels were significantly higher in comparison with the normal group (16.50 +/- 3.76 and 2.71 +/- 0.99 mm Hg; P=0.018 and 0.022, respectively). The mean peak IOP observed in the WDT was significantly higher than the IOP in the supine position (19.29 +/- 4.10 vs. 17.32 +/- 4.66 mm Hg, P=0.013). The mean IOP increase during the WDT was also significantly higher when compared with the postural test (4.13 +/- 2.33 vs. 2.84 +/- 2.21 mm Hg, P=0.019).Conclusions:POAG eyes demonstrated a significant IOP increase when assuming the supine position and during the WDT. The IOP increase during the WDT was significantly higher than the IOP increase after postural test. Hence, the results of both tests are not interchangeable.