• Written By: Jeffrey Freedman, MD, BCh, PhD, FRCSE, FCS

    This editorial discusses the potential use of the water drinking test for the diagnosis and treatment of patients with apparently normal IOP who demonstrate optic nerve pathology and visual field loss. The authors note that while the test's low sensitivity and specificity makes it unhelpful diagnostically, recent work points to its potential as a predictor of peak circadian IOP and IOP fluctuation. It may also prove useful for assessing the efficacy of treatment.

    During the water drinking test, the patient drinks a sizable quantity of water during a short period. IOP before and some time afterward is compared. Although the physiology of the test is not fully understood, its results have been shown to correlate well with peak pressures obtained using diurnal tension curve measurements.

    An age-old test that is easy to perform, it stresses outflow capabilities during a short period of time. Peak pressures measured with the water drinking test are higher in glaucomatous eyes with damaged outflow systems and more marked in eyes with progressive rather than stable glaucoma.

    I learned during my residency that the water drinking test is far less tedious to perform than diurnal curve measurement both for patients and physicians. The editorial's authors are to be congratulated for making us aware of this long-forgotten but potentially very useful glaucoma management tool. However, they note that further research on the test is needed.