PLASMINOGEN IN PROLIFERATIVE VITREORETINAL DISORDERS

Objective-Intravitreal fibrin formation is a frequent observation afte r vitrectomy performed for a variety of vitreoretinal disorders includ ing proliferative vitreoretinopathy (PVR), proliferative diabetic reti nopathy (PDR), and endophthalmitis. Plasminogen activators (PA) have b een used for the management of this postoperative complication. This a pproach requires the presence of plasminogen, the substrate for PA med iated fibrinolysis, in the vitreal cavity. Methods-Quantification of p lasminogen in the vitreous of 60 patients with PVR, PDR, and macular p ucker was performed by streptokinase mediated activation using a chrom ogenic substrate. The presence of immunoreactive plasminogen was confi rmed by immunoblot analysis of vitreal proteins and immunocytochemistr y of surgically removed epiretinal membranes. Results-Plasminogen leve ls were dramatically increased in the vitreous of PVR and PDR patients compared with macular pucker patients and normal controls. Staining f or plasminogen in epiretinal membranes was confined to the extracellul ar matrix. Predominant staining of perivascular areas in PDR specimens indicated that breakdown of the blood-retinal barrier is an important source of intravitreal plasminogen in that condition. Conclusion-Plas minogen may play a role in traction membrane formation in PVR and PDR. Our biochemical analysis of presurgical vitreous indicates that there may be abundant substrate for PA mediated fibrinolysis in the vitreou s cavity after vitrectomy.