PHASIC VARIATIONS IN TONOGRAPHY

Abstract

IN THE Proctor Lecture of 1951, Duke-Elder¹described three main types of phasic variation of the intraocular tension in simple glaucoma. These were, first, the falling type of curve, occurring in 20% of cases, in which the tension was highest early in the morning; second, the rising type, occurring in 25% of cases, in which the tension was highest in the late afternoon, and, third, the double variation, or biphasic type, occurring in 55% of cases, in which there were two peaks, one in the forenoon and the other in the late afternoon. He noted that simple glaucoma was a state "characterized initially by an instability of the ocular tension which shows a diurnal phasic variation of more than 5.0 mm. Hg." Grant,²in 1950, described his technique for tonography in detail and discussed its theory and application. As he stated, his work was based on the calculations