FIBRINOLYTIC-ASSISTED REMOVAL OF EXPERIMENTAL SUBRETINAL HEMORRHAGE WITHIN 7 DAYS REDUCES OUTER RETINAL DEGENERATION

Purpose: To better determine the surgical window for removing experime ntal subretinal hemorrhages in the cat model and to compare the histop athologic effect of such removal with the natural history of untreated subretinal hemorrhages.Methods: Twenty-three large experimental subre tinal hemorrhages were created with a neodymium:YAG laser focused thro ugh a preformed retinal bleb in a cohort of cats. Fourteen subretinal hemorrhages were observed without treatment, six were removed at 7 day s through a micropipette after injecting 10 mu g/ml of human recombina nt tissue plasminogen activator (rt-PA) into the subretinal space, and three were removed through an access retinotomy without the use of rt -PA. The tissues from these eyes were examined with light and electron microscopy 14 to 28 days after creation of the subretinal hemorrhages . Results: Severe outer retinal degeneration was evident by day 14 in all of the untreated subretinal hemorrhages 3 disc diameters or greate r in size. In contrast, the outer retinal architecture was better pres erved in the eyes that underwent rt-PA-assisted removal of their subre tinal hemorrhage that was 3 disc diameters or greater on day 7. In the se eyes, mild abnormalities such as abnormally short and misaligned ph otoreceptor outer segments with vacuolization were present within the retina that was formerly located over the hemorrhage center. The eyes that underwent subretinal hemorrhage removal through an access retinot omy without rt-PA on day 7 had a low-lying retinal detachment and oute r retinal degeneration. Conclusion: Removing experimental subretinal h emorrhages within 7 days of their occurrence with the assistance of rt -PA and an ultramicrosurgical approach may reduce outer retinal degene ration in the cat model.