Fig. 4. Flow diagram depicting possible mechanism of development of proliferative vitreoretinopathy. ILM, internal limiting membrane; FGF, fibroblast growth factor; RPE, retinal pigment epithelia; PDGF, platelet-derived growth factor; TGF-beta, transforming growth factor-β; PVR, proliferative vitreoretinopathy.* Fibronectin is an integral component of extracellular matrix and is a potent stimulator of cellular migration and proliferation of many cells. Fibrin typically occurs in postvitrectomy PVR patients who have had extensive anterior dissection and manipulation of the iris.