[Experimental retinal vein occlusion induced by photodynamic approach].

OBJECTIVE: To develop a new photochemical method of experimental retinal vein occlusion and investigate the morphologic and histologic changes in the retina. METHODS: After intravenous injection of rose Bengal, the vessels next to the disc of miniature pigs in the experiment group (n = 15) were exposed to an endo-illuminator for 15 minutes. As a control group, the vessels next to the disc of each pig were exposed to the endo-illuminator without rose Bengal injection. After complete vascular occlusion, the eyes were observed at following times: one hour, and 1, 3, 7, 14, 21, and 28 days. After the 28th day, the eyes were enucleated and prepared for light and electron microscope examination. RESULTS: Histopathologic features were consistent with changes of retinal vein occlusion and formation of retinal vein thrombi was reliable. CONCLUSIONS: Photodynamic method combined with endo-illuminator was a simple, reliable and definitive experimental technique to produce retinal vein occlusion.

[Experiment study of infusing tPA in retinal vein for treatment of retinal vein occlusion].

OBJECTIVE: To Investigate the effectiveness and complications of injection of tissue plasminogen activator into a retinal vein for treatment of retinal vein occlusion via micropuncture of the retinal vein. METHODS: Thirty miniature pigs (one eye of each pig) were produced photodynamic thrombi of retinal vein by injecting Rose bengal (20 mg/kg) into the ear vein, and randomly divided into three groups: 1. control (n = 8), 2. infusion of sterile water (n = 8) or 3. infusion of tissue-type plasminogen activator (n = 14) in obstructed retinal vein. In the first group no micropuncture of retinal vein was performed. In the others micropuncture of retinal vein were performed by a micromanipulator that we designed and sterile water was infused in retinal vein in the second group or tissue-type plasminogen activator was infused in the third one. Fluorescent angiography and histological study were performed to document the morphological alterations with clinical observations. RESULTS: 18 eyes were successfully performed micropuncture of retinal vein in the 22 eyes (81.4%). Except stopping operation due to surgical accident, there were 7 eyes that the thrombi were lysed in 9 eyes by infusion of tissue-type plasminogen activator in obstructed retinal vein (77.8%). If the micropipette was not accurate for puncturing the vessels, the vessels' wall could be ruptured and hemorrhage appeared. If thrombi of retinal veins were lysed, no bleeding and no leakage of the infused drug were observed from the site of micropuncture after micropipette was withdrawn from the vessel. Sterile water failed to flush the clot downstream. When the thrombus failed to be dislodged, the infusion fluid would back flow into the distal retinal vein and, an exudative retinal detachment would occur. In the first group, the retina exhibited hemorrhages and edema due to the vein occluded. In the second group, sterile water resulted in exaggerated retinal edema and exudative retinal detachment. In the third group, after thrombi of retinal veins were lysed, the hemorrhages and edema of retinal tissues were reduced significantly in few days. CONCLUSIONS: Infusing thrombolytic agents into the thrombosed retinal vein is a new method for treatment of retinal vein occlusion. This surgery must performed accurately by a special design. This study demonstrated that the rate and dose of thrombolytic agents infused in retinal vein should be limited in case of injuring retina tissues.