Enzyme-assisted vitrectomy with bacterial collagenase. Time course and toxicity studies.

Electron microscopic analysis of intravitreal strands produced by the injection of autogenous fibroblasts showed thin, immature collagen after two weeks and the mature banded variety after four weeks. With the use of this intravitreal strand model, it was found that highly purified bacterial collagenase caused extensive digestion of scar tissue after incubation periods of 10, 15, and 30 minutes. There was no morphologic damage to cicatricial cellular elements or to the inner limiting membrane of the retina. A 45-minute exposure of retinas previously injured by photocoagulation to collagenase also did not result in morphologic evidence of damage. The use of collagenase as an adjunct to vitrectomy in cases of extreme vitreal scarring or retinal traction may decrease the complication rate of a procedure that is still extremely hazardous.