Following water-drinking test, there is in the normal eye a statistically significant increase in applanation pressure, Schiøtz pressure, and frequency of Po/C ratio greater than 100. There is also a statistically significant reduction in the tonographic C value and in ocular rigidity. The magnitude of these effects varies significantly with age, with sequence of tonography, and with initial PA reading. Failure to control these variables in the clinical situation leads to a marked increase in the false positive error greatly reducing the possible usefulness of the test.
Armaly MF, Sayegh RE. Water-Drinking TestII. The Effect of Age on Tonometric and Tonographic Measures. Arch Ophthalmol. 1970;83(2):176-181. doi:10.1001/archopht.1970.00990030178009