The aim of the present study was to quantify and compare the vitreolytic effect of plasmin, hyaluronidase, and a combination of the two.

Thirty-six rabbits were randomized into 3 groups: (A) twelve rabbits had an intravitreal injection of plasmin 1 U with hyaluronidase 10 U/0.1 mL into the right eye, (B) twelve rabbits had an injection of plasmin alone (1 U/0.1 mL), and (C) twelve rabbits had an injection of hyaluronidase alone (10 U/0.1 mL). The left eye of each rabbit was used as control, which was injected with 0.1 mL phosphate buffered saline (PBS). The eyes were enucleated 1 hour and 24 hours after injection. The volume of fluid-type vitreous and gel-type vitreous was measured with a micropipette using the melting point as the difference. Statistical analysis was performed and light microscopy was used to assess potential damage to the retinal tissue.

The volume of remaining gel-type vitreous was measured as 52.5%, 60.3%, 59.2%, and 76.5% after 1 hour enucleation and as 44.6%, 56.7%, 56.1%, and 74.7%, after 24 hours enucleation in group A, B, C, and control group, respectively. Group A, B, and C showed statistically significant differences against the control group. Group A (plasmin with hyaluronidase) showed less remaining gel-type vitreous volume than a single injection of plasmin or hyaluronidase alone.

Intravitreal injection of plasmin with hyaluronidase showed more vitreolytic effect than a single injection of plasmin or hyaluronidase alone. The enzyme may be useful in liquefying the vitreous, and may be a useful biochemical adjunct to vitrectomy.