Effects of tissue plasminogen activator on glaucoma filter blebs in rabbits

Tissue plasminogen activator (tPA), a zymogen associated with fibrinolysis, was used in an attempt to prevent scarring and the consequent loss of glaucoma filtration blebs. Bilateral trephine filter procedures were performed in 10 new Zealand white rabbits. In a randomized, masked fashion, one eye received intracameral tPA (25 micrograms), and the fellow placebo, immediately following surgery. One week after surgery, outflow facility in the tPA-treated eyes was significantly greater than that in the control (P less than 0.01). Two weeks after surgery, the outflow facility returned to preoperative levels in all eyes. Eyes receiving tPA had larger blebs than the controls. No increase in postoperative complications, such as hemorrhage or wound leak, was attributable to tPA use. The results suggest that tPA interferes with the wound healing process after surgery and may promote glaucoma filter bleb formation.