EFFECT OF EPINEPHRINE ON LOCAL PARTIAL-PRESSURE OF OXYGEN IN THE CILIARY PROCESSES

Local pO(2) was measured close to the ciliary process of the rabbit ey e using polarographic microelectrodes under microendoscopic observatio n. The experiments were performed in 5 anaesthetized New Zealand rabbi ts. Changes in local pO(2), intraocular pressure (IOP) and blood flow velocity (BFV) were investigated after intra-arterial and topical appl ication of epinephrine. After intra-arterial epinephrine, a simultaneo us decrease in BFV, IOP and local pO(2) was found. pO(2) decrease was more pronounced in the anterior part of the ciliary processes than in the posterior part. Topical epinephrine lead to similar changes of all parameters mentioned abo;ve, the time constants being 10-20 times lon ger; In these topical experiments, no recovery of local pO(2) was foun d over a period of at least 30 min despite an increase in BFV. Our res ults indicate that in the hyperemic phase after epinephrine the activi ty of the ciliary epithelium (and probably the total aqueous formation ) is higher than normal. Thus, the decrease in IOP in this phase must be due to an increased outflow facility.