Best combination of plasmin and hyaluronidase in inducing posterior vitreous detachment

Objective To discuss the efficacy and safety of plasmin and hyaluronidase in inducing the posterior vitreous detachment(PVD),determine the best combined concentration of plasmin and hyaluronidase and provide the basis in choosing the drug dosage for further cataract model after vitreolysis by medicine.Methods Eighteen healthy SD rats were randomly divided into group A,B,C,6 rats in each group,their right eyes were set as experimental eyes and the left eyes as control.The intravitreal injection of 0.15 U plasmin plus 5 U hyaluronidase were performed in the right eyes in group A,0.25 U plasmin plus 5 U hyaluronidase in group B,0.50 U plasmin plus 5U hyaluronidase in group C,all the left eyes were injected with balance salt solution 10 μL.All the eyes were observed by slit-lamp biomicroscope and direct ophthalmoscope before and after intravitreal injection.The eyeballs were selected at 7 days after injection,and scanning electron microscopy and light microscopy were performed to observe the structure of inner limiting membrane and retina.Results No significant inflammatory response was detected by slit lamp biomicroscope in all right eyes of each group.Scanning electron microscopy results showed that certain degree PVD was found in all right eyes of each group,the partial PVD appeared in 5 eyes and complete PVD in 1 eye in group A,partial PVD in 2 eyes and complete PVD in 4 eyes in group B,and complete PVD in 6 eyes in group C.No PVD was appeared in all left eyes.The total rate of complete PVD in the right eyes of group A,B,C was 61.1%,there was significant difference compared with that of the left eyes(P0.001).The rate of complete PVD in the right eyes of group C was 100%,which in group A was 16.67%,there was statistical difference between them(P=0.015).There was no abnormal change of retinal structure in all injected eyes of each group by light microscope.Conclusion Intravitreal injection of 5 U hyaluronidase combined with 0.5 U plasmin has the most effect in producing vitreous liquefaction and complete PVD without intraocular toxicity.