A tudy of the ability of tiue plaminogen activator to diffue into the ubretinal pace after intravitreal injection in rabbit

PURPOE: Intravitreal injection of tiue plaminogen activator have been ued to lye fibrin from blood in the ubretinal pace, depite the lack of proof that tiue plaminogen activator can diffue acro the retina. We teted whether tiue plaminogen activator injected into the vitreou could penetrate the neural retina and enter the ubretinal pace. METHOD: We injected a mixture of 50 μg of tiue plaminogen activator (70 kD) labeled with fluorecein iothiocyanate and rhodamine B iothiocyanate–labeled dextran, which ha a lower molecular weight (20 kD), into the midvitreou cavity of one eye in each of 18 rabbit. The eye were enucleated after 3, 6, and 24 hour, and cryoection were examined with epifluorecent microcopy to determine the ditribution of the labeled molecule. We alo evaluated tiue plaminogen activator pharmacokinetic in one eye each of 18 rabbit in which a ubretinal clot wa induced by injecting autologou blood (50 μL) into the ubretinal pace through the clera. Fluorecein iothiocyanate–labeled tiue plaminogen activator wa injected into the vitreou 2 day after induction of the ubretinal clot. REULT: Fluorecein iothiocyanate–labeled tiue plaminogen activator wa preent at the vitreal urface of the retina in a linear array in all 36 eye tudied, wherea the rhodamine B iothiocyanate–labeled dextran had diffued throughout the neural retina in the ame ection. No fluorecein iothiocyanate ignal wa oberved in the neural retina or in the ubretinal clot. Vitreou hemorrhage caued by retinal perforation wa oberved in all eye with intraretinal hemorrhage in which fluorecein iothiocyanate fluorecence wa een in the neural retina and inide the clot. CONCLUION: Intravitreal tiue plaminogen activator did not diffue through the intact neural retina to reach a ubretinal clot. Thi tudy demontrate no cientific rationale for the intravitreal tiue plaminogen activator treatment of ubmacular hemorrhage without vitreou hemorrhage preumably caued by an overlying retinal break