Diurnal Tension Curve (DTC) and Water Drinking Test (WDT) - Covered by Manitoba Health
Eye pressure varies throughout the day. Often, our office pressures don't give us a good idea of what's happening over the course of the day. If a patient is getting worse even though the eye pressures seem to be normal at the visit, there may be other factors affecting the glaucoma (like low blood pressure or sleep apnea), or the eye pressures may be spiking outside office hours when we are unable to measure them.
In order to test for this, we can do either a DTC or a WDT.
The DTC (Diurnal Tension Curve) is usually performed by the technicians or Dr. Buffie, and requires a quick eye pressure check every hour throughout the day or half-day (mini-DTC). This is a long day or half day, however, we encourage patients who have this test to take the day off and enjoy the amenities of the mall in between pressure checks. The pressure checks will require freezing drops each time (since freezing only lasts for about 10-15 mins) and should not take longer than a few minutes on each hour. A DTC is usually scheduled throughout the day (or half-day) from 8:30 to 4:30.
The WDT (Water Drinking Test) is a stress test that is done over an hour or so. We ask that you refrain from drinking any liquids 2 hours prior to the test. At the office, we will give you 800 ml (just under a litre) of bottled water to drink in 5 minutes. We will take the pressure prior to drinking water and then every 15 minutes up to an hour or until the pressure starts to come down. If the eye pressure goes up, this indicates that your glaucoma may need more treatment. (If your eye pressures go up with this test, you can still drink water/ liquids as usual; just do not drink large volumes of liquids very fast).
Both these tests helps us determine if there are higher pressures or a tendency for higher pressure throughout the day which we might be missing at the office visit. This will help us make sure you are adequately treated for your glaucoma.