An experimental study on plasmin and dispase inducing posterior vitreous detachment

Objective To investigate whether an injection of plasmin and dispase can induce posterior vitreous de- tachment(PVD).Methods 24 young pigmented rabbits were assigned to four groups.All the right eyes were injected protnases.Eyes in group A received a vitreous injection of 1 unit of plasmin;Eyes in group B received a vitreous injection of 2 unit of plasmin;Eyes in group C received a vitreous injection of 0.0125 unit of dispase and Eyes in group D received a vitreous injection of 0.025 unit of dispase.24 left eyes were injected 0.1 ml BSS as controls.The eyes of rabbits were ob- served with biomicruscopy,B-ultrasonography and electroretinogram(ERG)in postinjection in vivo and were examined by light microscopy,scanning and transmission electron microscopy in vitro.Results In group B and C eyes,the retinal sur- face was smooth except for the vitreous base,indicating complete PVD(66.7%).In group A,eyes indicated partial PVD (33.3%)and in group D,eyes indicated complete PVD(83.3%).In the all control eyes,no PVD.The b-wave ampli- tudes of ERG showed no evident difference compared with preinjection in plasmin-group eyes and control eyes values in in- jected eyes(P0.05).Transmission electron microscopy and fight microscopy confirmed the retinal was not damaged.In dispase-gronp eyes,cellar edema and degeneration was present in retina and the b-wave amplitudes of ERG were signifi- cantly changed after the injection.Conclusion Vitreous injection of plasmin in dose of 2U can efficiently induce complete posterior vitreous detachment(PVD)without retinal toxicity compared with eyes received a vitreous injection of plasmin in dose of 1U.Although vitreous injection of dispase can efficiently induce complete posterior vitreous detachment(PVD), the retina was damaged.