Purpose: Intravitreal plasmin creates a posterior vitreous detachment, but may also liquefy the vitreous. This study measures the rate of vitreous removal from rabbit eyes after plasmin injection in vivo.
Methods: Intravitreal injections of 150 IU hyaluronidase (n = 5), 0.5 activity units (AU, n = 6) or 0.9 AU of streptokinase-activated human plasmin (n = four groups of 6) in 0.1 ml were performed in rabbits, the fellow eyes received 0.1 ml BSS. After 30 min (hyaluronidase), 30 min, 4 h, 12 h or 24 h (0.9 AU plasmin) or 24 h (0.5 AU plasmin), 1 ml of vitreous was removed from each eye without infusion, using a 25-gauge cutter and a standardized protocol. Animals were sacrificed after surgery.
Results: Compared to fellow eyes, the average rate of vitreous removal was increased by hyaluronidase by 68.9 +/- 6.3% (p < 0.05) and by 0.5 AU plasmin (24 h) by 26.8 +/- 3.3% (p < 0.05). 0.9 AU of plasmin increased removal rates by 0.8 +/- 10% (n.s.), 15.4 +/- 6.3% (p < 0.05), 40.3 +/- 3.1% (p < 0.05), and 71.9 +/- 32.4% (p < 0.05) after 30 min, 4 h, 12 h and 24 h incubation respectively. The ratios of removal rates of treated/control eyes in the 0.9 AU groups showed a linear correlation with incubation time (r = 0.783, p < 0.0001).
Conclusion: Intravitreal plasmin increases the rate of vitreous removal in rabbits.