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Editors Selection IGR 9-4

Intraocular Pressure: Waterdrinking test and longterm IOP variation

Comment by Arthur Sit on:

23699 Agreement between stress intraocular pressure and long-term intraocular pressure measurements in primary open angle glaucoma, De Moraes CG; Furlanetto RL; Reis AS et al., Clinical and Experimental Ophthalmology, 2009; 37: 270-274

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Long-term intraocular pressure (IOP) variations over months to years have been implicated as possible risk factors for glaucoma progression independent of mean IOP. However, the only way to assess these variations is to periodically measure IOP and assess the variations retrospectively. De Moraes et al. (627) investigated the possible use of the water drinking test (WDT) to estimate longterm IOP variations. The water drink- ing test (WDT) involves the Long-term intraocular pressure (IOP) variations over months to years have been implicated as possible risk factors for glaucoma progression independent of mean IOP. However, the only way to assess these variations is to periodically measure IOP and assess the variations retrospectively. De Moraes et al. (627) investigated the possible use of the water drinking test (WDT) to estimate longterm IOP variations. The water drink- ing test (WDT) involves the ingestion of 1 L of water over a 5-minute period, inducing a transient elevation of IOP. This effect has long been known, but the WDT has had a recent resurgence in interest as a surrogate measure of both short and long-term IOP peaks and variations. In this study, De Moraes et al. assessed the relationship between IOP peaks and fluctuations during a WDT with those occurring during routine office IOP measurements. In their study, a group of 22 newly diagnosed primary open angle glaucoma patients had a WDT performed 4 weeks after starting medical therapy. IOP was then measured 8 times during office hours over the next 6-12 months. The authors compared the results using Spearman correlations and Bland-Altman plots.

IOP peaks and fluctuations in the WDT are correlated with long-term IOP peaks and fluctuations

The results of this study provide compelling evidence that IOP peaks and fluctuations in the WDT are correlated with long-term IOP peaks and fluctuations measured during office hours in medically treated glaucoma patients. However, the clinical significance of long-term IOP fluctuations remains unclear. Previous research examining the data from the Advanced Glaucoma Intervention Study (AGIS) suggested that long-term IOP fluctuations were a risk factor for glaucoma progression.¹ However, subsequent studies from the Early Manifest Glaucoma Trial (EMGT) and the Diagnostic Innovations in Glaucoma Study (DIGS) failed to find a relationship between glaucoma progression and long-term IOP fluctuations.^{2, 3} As well, the mechanism of action of the WDT remains unclear, although previous work from De Moraes et al.⁴ has suggested choroidal expansion as one possible mechanism.

The clinical significance of longterm IOP fluctuations remains unclear

The authors concluded that stress tests such as the WDT could be used to estimate long-term IOP variation. Future work will be needed to determine the clinical utility of these measurements. Nevertheless, the potential ability to predict long-term IOP fluctuations in newly diagnosed glaucoma patients is certainly deserving of further investigation.

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