We read with great interest the editorial by Goldberg and Clement on the water drinking test. The authors reviewed relevant studies on this topic. We would like to highlight some important points that may complement their editorial and may be clinically relevant to your readership.

First, it is important to emphasize that the reason for performing the water drinking test has changed from it being a test once thought useful in predicting which ocular hypertensive patients were more prone to develop visual field loss to a stress test to assess the capacitance of the trabecular meshwork. Similarly to other widely used stress tests (eg, glucose tolerance test or cardiac stress test), the aim is to stress the trabecular meshwork and to observe how high the intraocular pressure rises and how long it takes to return to baseline. Rather than a specific numerical rise in intraocular pressure constituting a positive test, its interpretation depends on each patient’s baseline intraocular pressure, level of damage, and rate of progression.

Although the physiology of the water drinking test is not fully understood, we have demonstrated that, at least in part, the intraocular pressure elevation may be caused by an increase in choroidal thickness resulting in a pressure gradient that is transmitted to intraocular compartments, causing aqueous to exit from the anterior chamber to the drainage system. Eyes may show a higher intraocular pressure elevation, depending on their outflow facility.

Second, the water drinking test may prove very useful in assessing the efficacy of clinical or surgical therapy on the prevention of intraocular pressure spikes. As Goldberg and Clement described, intraocular pressure peaks detected during the water drinking test seem to correlate well with the peaks detected during diurnal tension curves. In this regard, the water drinking test may have an important role in the assessment of the quality of treatment and the probability of progression.

Third, the water drinking test may differentiate between drugs that can produce equivalent intraocular pressure reductions in steady-state situations, but that may have different abilities to dampen intraocular pressure peaks, as showed by Susanna and associates. Medications capable of preventing greater or undetected intraocular pressure peaks, or both, may have an additional benefit in glaucoma treatment.

Finally, we believe that there is an important potential role for the usefulness of this test in glaucoma management, and for this reason, it deserves to be investigated more widely.