Yassein HA, Hamdi MM, Abdelshafik MA and Galal AS
Purpose: To assess the relations between the intraocular peaks detected during water drinking test (WDT) and modified diurnal tension curve (mDTC) in glaucomatous and non-glaucomatous eyes. Likewise to assess reliability of WDT as a reliable substitute. Patients and methods: Forty eyes from forty participants (21 males and 19 females) were recruited in this prospective cross-sectional study; twenty participants with known Primary Open Angle Glaucoma and the other twenty participants with non- glaucomatous healthy eyes which served as control. Four IOP measurements were taken at 8:00 am, 12:00 pm, 4:00 pm and 8:00 pm which represented the mDTC, while WDT was represented by a single measurement of IOP before ingestion of one liter of water over five minutes, followed by three IOP measurements after ingestion of this amount of water at thirty minute intervals. The data collected were statistically evaluated using the statistical package for social science (SPSS) program for presence of a correlation between the two methods. Results: The IOP peaks and fluctuations detected during the WDT were strongly correlated to peaks and fluctuations observed during the mDTC. 90% of participants had a peak IOP at 8:00 am, while 7.5% had a peak IOP at 12:00 pm, 2.5% at 4:00 pm and none of the participants had IOP peak at 8:00 pm during the mDTC. In the WDT, 87.5% of the participants had a peak IOP after 30 minutes of ingesting one liter of water, while 12.5% had a peak IOP after 60 minutes. None of the participants had IOP peak after 90 minutes of ingesting one liter of water. IOP fluctuation in mDTC ranged from: 1-4.5 mmHg in 95% of normal participants, 7-11 mmHg in 83.3% of glaucoma suspects, 1.5-5 mmHg in SST subgroup and 4-11 mmHg in the glaucoma on medication subgroup. There were relatively similar results in the WDT fluctuation, whereas 38 cases out of 40 (95%) showed a difference of ± 2 mmHg or less between the two methods. Conclusion: Intraocular pressure peaks and fluctuations detected during the water drinking test could be used in clinical practice to estimate the peaks and fluctuations observed during the modified diurnal tension curve.