The canine eye: in vitro studies of the intraocular pressure and facility of aqueous outflow.

Possible interdependence of facility of aqueous outflow and intraocular pressure was examined by quantitative aqueous perfusion at four levels of intraocular pressure in 69 canine eyes, freshly excised post-mortem. Statistically similar, time-dependent increases in facility of outflow occurred over steps of increasing and decreasing, and at constant intraocular pressue. Pretreatment with intracameral hyaluronidase diminished the rate of facility increase, reducing it to 20% or less in one third of the eyes so perfused. Observed increases in canine facility of outflow with changing intraocular pressure appeared to result primarily from "washout" of the hyaluronidase-sensitive component of the barriers to aqueous outflow and not from direct effects of the intraocular pressure.