Effects of Na2EDTA and Alpha-chymotrypsin on Aqueous Humor Outflow Conductance in Monkey Eyes

Abstract

In glaucoma there is partial clogging of the outflow routes for aqueous humor between the anterior chamber and the canal of Schlemm. In monkeys chelating agents perfused from the anterior chamber markedly reduce the outflow resistance, but the effect is short-lasting. In the present study an attempt was made to prolong the effect of Na₂EDTA with alpha-chymotrypsin and the effect of this agent alone was also tested. After 30 min of perfusion with 50 U/ml alpha-chymotrypsin there was a marked rise in outflow conductance, which was well maintained during subsequent perfusion without the enzyme. Two hrs after enzyme perfusion the rise in outflow conductance was 1.25±0.20μl·min⁻¹·cm H₂O⁻¹ from a starting level of 0.33±0.08μl·min⁻¹·cm H₂O⁻¹. In eyes perfused with alpha-chymotrypsin and 0.5 mmol/l Na₂EDTA in ⁺⁺Na- and ⁺⁺Mg- free perfusate for 30 min the rise in outflow conductance observed 2 hrs later was 1.72±0.20μl·min⁻¹·cm H₂O⁻¹. No adverse effects were observed in the eyes during the experiments and the next few weeks. The results indicate that perfusion with alpha-chymotrypsin produces relatively wide routes for aqueous drainage into the canal of Schlemm, which remain patent at least for several hours. In addition the enzyme seems to prolong the effect of Na₂EDTA