Gross Facility, Facility of Conventional Routes, and Pseudofacility of Aqueous Humor Outflow in the Cynomolgus Monkey

There is no doubt that to a large extent the aqueous humor is formed by a secretory mechanism that delivers fluid into the posterior chamber from the ciliary processes. The posterior chamber aqueous humor exchanges with the surrounding tissues,¹and we do not know if this gives a net loss of aqueous humor volume or a gain before the fluid enters the anterior chamber by bulk flow. In the cynomolgus monkey the bulk outflow from this chamber, which may include some pinocytosis, occurs in part by way of Schlemm's canal into the general circulation (conventional outflow), and in part by way of uveoscleral routes into the episcleral tissues.²,³The outflow through the conventional routes is pressure dependent, that is, it increases with an increase in intraocular pressure; the uveoscleral drainage, on the contrary, is very little, if at all, influenced by a moderate increase in intraocular pressure above