T.M.
I haven't heard of this in dogs, but my grandmother had it and we had a friend who's son had it. Grandma's was in her lungs and never spread, but if I remember right she would test positive for TB. My friends son lost his sight, not totally, but he only had peripheral vision, he couldn't see straight ahead, only to the side. Good Luck, I'm afraid his age might be a factor, give the med's time to work, some don't work completely until a few days after they are finished. He just might need a few days to recuperate.