Influence of intraocular pressure on aqueous outflow facility in enucleated eyes of different mammals.

Freshly enucleated monkey, calf, and human eyes were quantitatively perfused with mock aqueous humor through the anterior chamber by a constant pressure technique. After baseline perfusion at 15 mm Hg, intraocular pressure was raised to 45 mm Hg and later reduced back to 15 mm Hg. Calf and human (both adult and infant) eyes had lower outflow facilities at 45 than at 15 mm Hg. However, four types of monkey eyes did not show decreased facility of outflow at elevated perfusion pressure, and after return of pressure to 15 mm Hg, facility of outflow actually increased compared to baseline, unlike both calf and human eyes. The results indicate that there are significant differences in the response of enucleated mammalian eyes to an elevation in perfusion pressure. Factors other than, or in addition to, collapse of Schlemm's canal may be important in the pathogenesis of the pressure-induced decrease in outflow facility found in human eyes.