Abstract
Abstract: :
Purpose: To quantify the relationship between ciliary blood flow and aqueous production under ganglionic blockade conditions in an animal model. Methods: In pentobarbital anesthetized rabbits, mean arterial pressure (MAP) and intraocular pressure were measured by direct cannulation. In Group 1 (n=28), aqueous flow was measured by fluorophotometry. In Group 2 (n=23), ciliary blood flow was measured by laser Doppler flowmetry. Measurements in both groups were made under ganglionic blockade conditions (hexamethonium, 50 mg/ml infused at 1.5 ml/hr) for 60 min while MAP was set at 30, 40, 55, 70 or 80 mmHg with occluders on the vena cava and aorta. Results: Ganglionic blockade causes ciliary vasodilation and shifts the ciliary pressure–flow relationship upwards; however, it does not markedly alter the relationship between ciliary blood flow and aqueous production (dashed line in figure shows control relationship from IOVS 2003;44:3967–3971). Conclusions: In the anesthetized rabbit under control conditions, aqueous production becomes blood flow–dependent when ciliary perfusion falls below 70% of its control value; at higher blood flow rates, aqueous production is independent of blood flow. Removal of autonomic neural input to the eye does not alter this relationship.
Keywords: blood supply • ciliary body • pharmacology