The water-drinking test was proposed decades ago as a means to diagnose glaucoma. The premise was straightforward. If glaucoma affects the drainage angle and impairs outflow facility, then the ability of eyes with glaucoma to handle a fluid challenge should be impaired. Following a baseline intraocular pressure (IOP) measurement, the subject quickly consumes one liter of water and undergoes subsequent IOP measurements every 15 minutes for one hour. Normal eyes should be able to handle the fluid challenge by increasing outflow, whereas a glaucomatous eye with impaired outflow would be less able to adapt to the fluid influx and thus should manifest an IOP rise. A rise in IOP of 6 to 8 mmHg or an increase from baseline of 30% or more at any time during the hour was considered a positive test.
New applications for an old test
“The eye with worse glaucoma manifested a higher IOP rise than the better eye, and the worse eye also took longer to recover to pre-test IOP baseline than the better eye,” he said. He pointed out that the water-drinking test challenged the eye and revealed relevant data that was not apparent in the unperturbed system. “Intraocular pressure hemostasis was worse in the worse eye.”
“The IOP peaks in the hour following the water-drinking test were higher in the group that had visual field progression compared to the group whose visual fields had remained stable,” he said. This suggests that the water-drinking test can predict which patients with open-angle glaucoma may be at higher risk of progression, he added.
“Peaks and fluctuations in IOP have been identified as important risk factors for glaucoma progression,” she said. “But detecting IOP peaks and fluctuation requires diurnal IOP measurement, which is difficult and expensive.”
“In the morning, mean IOP rose from 14.3 mmHg to a peak of 17.3 mmHg, while in the afternoon, IOP rose from 12.7 mmHg to 16.8 mmHg,
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