My guess is fibromas. They're wart-like tumors. Fibromas attach to skin only, not muscle. They're generally not deadly but it looks like this buck's going to lose his sight because of the growths. It's unusual for fibromatosis to spread this badly. It's caused by a virus. Fibromas usually stop growing while they're small and sometimes heal and disappear. Since this is a virus, the deer will develop some immunity.