PVD following plasmin but not hyaluronidase: implications for combination pharmacologic vitreolysis therapy

To study whether intravitreal injection of plasmin + hyaluronidase safely induces posterior vitreous detachment (PVD).Rabbits were randomized into three groups: (A) 20 rabbits, intravitreal injection of plasmin 1 U + hyaluronidase 20 U in balanced salt solution (BSS) 0.1 mL into one eye; (B) 12 rabbits, plasmin alone; (C) 12 rabbits, hyaluronidase alone. The fellow eye of each rabbit was injected BSS 0.1 mL. In Group A, scanning electron microscopy (SEM) was done in four rabbits at 0.5 hour and in four rabbits at 1 hour. After 7 days, all the remaining 36 rabbits received electroretinography, SEM was examined in eight of each group, and immunohistochemistry was done in four of each group.SEM disclosed the eyes of Group A had complete PVD (8/8), Group B partial PVD (7/8), and Group C (8/8) and all the control eyes (24/24) no PVD after 7 days. Partial PVD was found in 4/4 at 0.5 hour and complete PVD was seen in 3/4 at 1 hour in Group A. Immunohistochemistry showed that the amounts of laminin and fibronectin in the vitreoretinal interface were decreased in Group A and B versus the control eyes (P0.001), but not in Group C versus the control eyes (P0.05). Electroretinography showed no changes in any group (P0.05).Vitreous injection of plasmin + hyaluronidase induced complete PVD with no obvious toxicity. Plasmin induced partial PVD, but hyaluronidase had no effects.