Aqueous Humor Dynamics in α-Chymotrypsin-Induced Ocular Hypertensive Rabbits

Aqueous humor dynamics were studied in alpha-chymotrypsin-induced ocular hypertensive rabbits either by tonographic or two-level constant pressure perfusion techniques. A significant correlation was obtained between the values of outflow facility in alpha-chymotrypsin-induced ocular hypertensive rabbits as determined by tonography and constant pressure perfusion. The mean value of tonographic outflow facility in ocular hypertensive rabbits was not statistically different from that found in ocular normotensive rabbits. On the contrary, the estimated rate of aqueous inflow in ocular hypertensive rabbits was about 1.5-fold higher than that of ocular normotensive ones. While topical timolol lowered intraocular pressure and aqueous humor inflow in ocular hypertensive rabbits, pilocarpine did not produce any significant effect. Aqueous humor protein was significantly increased in ocular hypertensive eyes. The results of this study show that accurate measurements of outflow facility can be obtained in alpha-chymotrypsin-induced ocular hypertensive rabbits by tonographic technique. Our data suggest that the long-term ocular hypertension induced by alpha-chymotrypsin in albino rabbits may be secondary to an increase in the rate of aqueous humor inflow, likely produced by a breakdown of the blood-aqueous barrier. This finding strongly conflicts with the hypothesis of trabecular blockage as the cause of alpha-chymotrypsin-induced ocular hypertension in this species.