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A new procedure for measuring the outflow facility in conscious rabbits is described. The Langham pneumatic tonometer is applied horizontally against the eye; the intraocular pressure (IOP) is recorded before, during and immediately following 2 min of a pre-determined increased ocular pressure that is maintained at a fixed value by digital pressure applied through the eyelids. An increased volume of aqueous humor outflow resulting from the IOP increase is evaluated from the initial and final IOP values and the pressure volume relation for eyes of living rabbits. Close agreement in values of the outflow facilities in pairs of eyes of individual rabbits and excellent reproducibility of the procedure were found in repeated measurements made over a 24-hr period. The mean values of the IOP and the total outflow facility in 60 eyes of 30 rabbits were 20.5 +/- 0.2 mmHg and 0.17 +/- 0.01 microliter min-1 mmHg-1 respectively. Thirty minutes after an intravenous injection of acetazolamide, the IOP had decreased in both eyes of individual rabbits. This was associated with a decrease in the outflow facility and with a decrease of more than 50% in the rate of aqueous humor formation. One hour after the unilateral application of epinephrine the IOP had decreased in the treated eyes while the outflow facility remained unchanged.

A new methodological approach, embodied in the pneumatonograph, has been used to study the intraocular pressure, intraocular pulse and aqueous humor dynamics of normal and glaucomatous eyes. Comparative measurements of intraocular pressure in seated subjects by the Goldmann instrument and the pneumatonograph indicate close agreement over a wide range of pressures. On changing from the sitting to the supine position, it has been found by pneumatonometry that there is a significant increase of intraocular pressure in all eyes. In glaucomatous eyes, this postural response ranged up to as high as 12 mm Hg. Comparison of Schiotz and pneumatonometric pressure measurements on supine patients showed that the Schoitz values are significantly lower. This discrepancy of the values is in keeping with recent studies indicative that the Schiotz calibration is in error by 3-6 mm Hg. The coefficient of outflow facility was measured by a procedure of applanation tonography employing pressure-volume relations for the living human eye. The range of values found for normal eyes was significantly different from those of glaucoma eyes. It is concluded that pneumatonography is a useful method for improving the effectiveness of glaucoma diagnosis and clinical management.