What is the treatment for blood draining behind the retina?

Depends on cause. Blood draining behind the retina is actually blood accumulating behind the retina. The medical term is subretinal hemorrhage. The treatment depends on the cause and amount. If it is due to trauma and central, affecting the vision, it can either be observed for clearing or surgically removed. If due to macular degeneration, it can be treated by intraocular injections. There are other causes.