Effect of subconjunctivally injected liposome-encapsulated tissue plasminogen activator on the absorption rate of subconjunctival hemorrhages in rabbits.

Purpose: To evaluate the effect of subconjunctivally injected liposome-encapsulated tissue plasminogen activator (tPA) on the absorption rate of subconjunctival hemorrhages (SHs).
Methods: SHs were induced in 1 eye each of 36 rabbits by subconjunctival injection of 0.05 mL of autologous blood. After 8 hours, randomized subconjunctival injections were performed: 26,000 IU/mL liposome-encapsulated tPA (0.05 mL) in 9 eyes (group A), free-form tPA (26,000 IU/mL; 0.05 mL) in 9 eyes (group B), only liposomes (0.05 mL) in 9 eyes (group C), or no injection in 9 eyes (group D). The sizes of the SHs at 8, 24, 48, 72, 96, and 120 hours after induction were measured using an image analyzer and were compared among the 4 groups.
Results: Group A showed significantly more rapid absorption rates than all the other groups at 24, 48, and 72 hours and had the significantly shortest mean elapsed time for the complete resorption of SHs. The tPA activity in ocular tissue except conjunctiva and plasma were negligible beyond 24 hours after SH induction with both forms of tPA. In the conjunctiva, the tPA activity was significantly prolonged in the liposome-encapsulated tPA group than in the free tPA group.
Conclusions: Subconjunctival injection of liposome-encapsulated tPA seems to enhance SH absorption in rabbits, especially during the early stages with minimal systemic and ocular absorption.