Fibrinolytic-assisted Removal of Experimental Subretinal Hemorrhage within Seven Days Reduces Outer Retinal Degeneration

Abstract

To better determine the surgical window for removing experimental subretinal hemorrhages in the cat model and to compare the histopathologic effect of such removal with the natural history of untreated subretinal hemorrhages. Twenty-three large experimental subretinal hemorrhages were created with a neodymium:YAG laser focused through a performed retinal bleb in a cohort of cats. Fourteen subretinal hemorrhages were observed without treatment, six were removed at 7 days through a micropipette after injecting 10 micrograms/ml of human recombinant 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. Severe outer retinal degeneration was evident by day 14 in all of the untreated subretinal hemorrhages 3 disc diameters or greater in size. In contrast, the outer retinal architecture was better preserved in the eyes that underwent rt-PA-assisted removal of their subretinal hemorrhage that was 3 disc diameters or greater on day 7. In these eyes, mild abnormalities such as abnormally short and misaligned photoreceptor 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 retinotomy without rt-PA on day 7 had a low-lying retinal detachment and outer retinal degeneration. Removing experimental subretinal hemorrhages within 7 days of their occurrence with the assistance of rt-PA and an ultramicrosurgical approach may reduce outer retinal degeneration in the cat model.