Further studies on the influence of the intraocular pressure on aqueous humor dynamics in cynomolgus monkeys

'1-albumin was used to determine the rate of bulk outflow from the anterior chamber in one eye and I-albumin was used in the other. In 16 eyes at a spontaneous intraocular pressure of 8.0 ± 0.7 mm. Hg, uveoscleral flow was 0.63 ± 0.08 nL per minute and flow by fast, vascular routes was 0.53 ± 0.07 fiL per minute. When the intraocular pressure was lowered to 2 or 4 mm. Hg by letting aqueous flow into a reservoir, drainage of anterior chamber fluid into the blood by way of fast routes stopped almost completely. At 2 mm. Hg the bulk flow into the uveoscleral routes was reduced by an average of 63 per cent, but at 4 mm. Hg uveoscleral flow was normal in 4 of 5 eyes. Adjusting the intraocular pressure from the spontaneous level to 35 mm. Hg by inflow from a reservoir gave an average outflow into the general circulation that was 12.0 ± 2.3 pL per minute higher than in the control eyes. Uveoscleral flow was not raised significantly. Pseudofacility was 0.055 ± 0.013 fiL per minute per millimeter Hg. In dead eyes uveoscleral flow appeared to be pressure sensitive in a wider pressure range than in living eyes. It is concluded that in cynomolgus monkeys aqueous humor passes out through the conventional vascular routes into the episcleral veins and passes out through uveoscleral routes that drain its high molecular components into the suprachoroid and the episcleral tissues. However, pinocytosis, in the uveal blood vessels} plays little role for bulk drainage of aqueous humor. In living cynomolgus eyes, within the range 8 to 35 mm. Hg, the intraocular pressure (IOP) is determined by the recipient venous pressure (Pv), the net rate of aqueous humor formation (Fn), the rate of aqueous outflow by uveoscleral routes (Fu), and the gross facility of outflow Co according to IOP = PB + (Fn Fu)/(Cg 0.06).