A functional study of the chamber angle in health and disease became a practical possibility in 1950 with the discovery that the rate of aqueous humor escape from the eye might be calculated by estimating the volume change induced during artificial elevation of the intraocular pressure by external application of a known weight to the eye.1,2 The tonographic procedure has since been extensively used both clinically and experimentally, although the assumptions upon which its validity depends have been frequently called into question.3 There is the problem of whether the volume change induced is entirely accounted for merely by the amount of fluid expressed through the chamber angle. Some of the volume change may include other components, such as expelled blood and scleral creep. If it is then assumed that the volume change is correctly accounted, there still remains the question of a constant secretory rate under tonographic pressure.
MARVIN L. SEARS. Outflow Resistance of the Rabbit Eye: Technique and Effects of AcetazolamideDetermination by Constant Rate Anterior Chamber Infusion in Vivo. Arch Ophthalmol. 1960;64(6):823–838. doi:10.1001/archopht.1960.01840010825003