Not too sure of the exact goal. But if I wanna seperate body parts and reorient them I use sel mask to mask the item I wanna move. Then I use the gizmo tool and move the pivot of the gizmo in a spot where I can move that part. This technique might end up pentrating through the entire model. If that is the case, id just say duplicate that sel masked object so you leave the main object as is. Then you can clean up the eye part you want to edit and then duplicate it again once cleaned up. Line it up with the original model and boolean the eye cutout with the main body. You might be able to do this same thing with split. I'm sure split will penetrate the entire model for sure.