In 1963, Bárány1 presented an elegant theoretical discussion of aqueous humor dynamics. The possible modes of aqueous formation included a pump or secretion of aqueous into the eye and an ultrafiltration of aqueous from the intraocular capillaries to the lower-pressure eye cavity. Bárány called the proposed pressure-dependent ultrafiltration "pseudofacility," since when trabecular outflow facility ("true facility") is measured by any procedure that elevates intraocular pressure (Pi) (perfusion of the aqueous space, tonography, perilimbal suction cup) the increased Pi diminishes the pressure head between blood and eye cavity and decreases the rate of aqueous formation by ultrafiltration; the decreased aqueous inflow could easily be confused with the increased aqueous outflow also resulting from the imposed Pi elevation, and hence would be a false facility or pseudofacility.
Stimulated by Bárány's theoretical discussion, Brubaker and Kupfer2 and Bill and Bárány3 searched for evidence of the formation of
Moses RA, Grodzki WJ, Carras PL. PseudofacilityWhere Did It Go?. Arch Ophthalmol. 1985;103(11):1653-1655. doi:10.1001/archopht.1985.01050110047021