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Lisia B. Ferreira, Luis Francisco B. Chotgues, Helena M. Pakter, Matha P. Lang, Egidio Picetti; Modified Water-Drinking Test: An Alternative Way to Estimate Morning IOP Peak in Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5050.
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To describe and compare the results of a modified water-drinking test (mWDT) to the intra ocular pressure (IOP) measured at waking up time in bed at home, and upon arrival at the clinic in glaucoma patients.
Forty-five adult glaucoma patients (90 eyes) participated in this cross-sectional study carried out from 2010 to 2011 at a glaucoma service in Porto Alegre, Brazil. Participants had their IOP checked by hand-held applanation tonometry between 6 and 7 am, at home, right after waking up while still lying in bed by the same ophthalmologist. Patients were assigned to a mWDT at 8 am at the glaucoma clinic. They were advised to previously fast for 1 hour and arrive 15 minutes before testing time in order to rest and avoid activities that could lead to accommodation. Patients would then drink 500ml of room temperature water in 5 minutes and the IOP was tested immediately after in a sitting position. Afterwards, they would lie down in supine position under dim light for 15 minutes in a quiet place before IOP was mensured again. IOP in bed at home (time zero - T0), the first IOP measurement right after drinking 500ml of water (time 1 - T1) and IOP measurement 15 minutes after mWDT in supine position (time 2 -T2) were verified. To test measurements reproducibility, a subset of 12 patients (24 eyes) had the entire procedure done twice, in a different day, by the same examiner.
There was no significant difference between IOP measured at T0 and T2 (pair t test mean difference -0.07 mmHg; 95% CI -0.6 to 0.5; p=0.80; Pearson correlation test 0.86). IOP measured at T0 was on average 5.36 mmHg (95% CI 4.65 to 6.08; p<0.05) higher than T1. IOP measured at T1 was on average 5.43mmHg lower (95% CI -6.02 to -4.84; p<0.05) than IOP measured at T2. Data reproducibility was very good for T2 (ICC 0.94) and T0 (ICC 0.80) but not for T1 (ICC 0.49).
Our results show that IOP verified at waking-up time in bed at home (T0) had excellent agreement with IOP assessed 15 minutes after mWDT (T2) in glaucoma patients and these measurements (T0 and T2) were reproducible. Early morning IOP peak, which has been considered a risk factor for glaucoma progression, could be very well estimated by our mWDT. This could be an easier, faster and reliable method to appraise morning IOP peak in glaucoma patients.
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