Intra-ocular fibrin deposition following ocular surgery is a serious postoperative complication. The current management of severe postoperative fibrin response is usually ineffective. A quantitative model of fibrin deposition in the rabbit anterior chamber was used to assess the efficacy of Suleparoide I.N.N. (HHS-5) in preventing fibrin formation and in promoting the clearance of fibrinous membranes. Citrated human plasma was injected intracamerally after paracentesis to induce the formation of fibrin clots: 10 min or 24 h after plasma injection, solutions of HHS-5 at different concentrations were injected into the anterior chamber of rabbits. Intra-ocular HHS-5 injection 10 min after plasma injection prevented the formation of fibrinous membranes in a dose-dependent fashion in almost all treated animals. When HHS-5 was injected at 24 h after fibrin clot formation, a reduction of clot areas was observed but the membranes did not completely disappear. No evidence of ocular toxicity was detected by slit-lamp bio microscopy, intra-ocular pressure and corneal thickness measurements. On the basis of the results obtained with the present animal model, HHS-5 appears as an effective and safe agent for the prevention of fibrinous membrane formation. The data suggest a potential use of HHS-5 for the prophylaxis of fibrin formation in human eyes undergoing extensive intraocular surgery, or in diabetic patients where a hypercoagulable state may be present.