It's the edge of the eyecap, as the others said. I helped Mrs. Snake get hers off the other day. The skin appears white around the eye b/c it has a fold in it. The eyecap is most likely still there, too. You can try the shed assist tutorial. Or use a little olive oil and a washcloth. Be very gentle with the eye, but IMHO, you should try to get it off if your snake can't do it on his own. Maybe wait until he digests first?