Time-dependence of perfusion outflow facility in the cynomolgus monkey

Surgically virgin (N), aniridic (I), and ciliary muscle disinserted (D) cynomolgus monkey eyes had total outflow facility determined in vivo for 88-136 minutes by two-level constant pressure perfusion of the anterior chamber. In all three types of eyes, facility increased during the first hour but stabilized thereafter. Average facility for the second half hour was 15% higher than for the first half hour in N and I eyes, and 10% higher in D eyes. Altered iris muscle tone can therefore not explain the facility increase, while increased ciliary muscle tone might explain part but not all of it. Judicious use of the data may aid interpretation of perfusion experiments conducted under similar conditions.