Ultrastructure Research of Posterior Vitreous Detachment

Objective:Through vitreous injection of plasmin or hyaluronidase,investigate the ultrastructural change of the vitreoretinal interface,and illuminate the mechanism of posterior vitreous detachment (PVD). Methods:Sixteen New Zealand white rabbits were assigned to three groups (8,4,4,respectively).In each group,the right eyes were experimental eyes and the left eyes were control eyes.Experimental eyes in group A received a vitreous injection of plasmin 1U combined with hyaluronidase 20U (0.1 ml reconstituted in balanced salt solution).Eyes in group B received vitreous injection of plasmin alone (1U/0.1 ml).Eyes in group C received hyaluronidase alone (20U/0.1ml).Seven days after injection,all the eyes were enucleated.After fixation,scanning electron microscopy was performed. Results:The diameter of the vitreous collagen fiber was 10～30 nm under scanning electron microscope.The remained vitreous cortex was closely adhered to the pits in the surface of inner limiting membrane (ILM).At the posterior pole or the equator,vitreous collagen ran parallel to ILM.In group A,all the eyes were induced complete PVD 100%(8/8).In group B,the partial PVD was 75%(3/4),one eye was complete PVD.In group C and all the controls,there were no PVD developed (0/4,0/8 respectively). Conclusions:The key for the drugs to induce the PVD,which can perform in clinic,is that they can both dissolve the adhesion between the vitreoretinal interfaces and liquefy the vitreous.Plasmin 1U combined with hyaluronidase 20U can induce complete PVD.