Thursday, December 22, 2005


Has anybody ever done the "water drinking test" to determine the peak of the diurnal IOP curve? According to the theory: "Fluctuations of IOP in glaucomatous patients can be induced by the osmotic variations caused by water ingestion. Such influence can be studied by means of the water-drinking test (WDT)" (J Ocul Pharmacol Ther. 2005 Jun;21(3):250-7.).

Here's how it's done: The patient drinks 4 cups of water in 10 minutes and the IOP is measured every 15 minutes until the pressure returns to baseline levels. On the chart you record the peak IOP, the percentage increase, and how long it takes to return to baseline.

According to one recent study, the higher the peak IOP and percentage change of IOP during the water drinking test, the greater the progression of visual field loss).

The first mentioned study above says that patients on Timolol, Trusopt, and Azopt reach a higher peak IOP and shorter return to normal than patients taking the prostaglandin analogues and Alphagan-P (the former affect aqueous production and the latter affect outflow). This would suggest Lumigan and Alphagan-P is better to decrease diurnal variations.

Is the water drinking test useful to us at all in the clinic? All I can say is, the bathroom better be nearby and unoccupied!

Dr. Kevin

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