My 15 year old dog just had a strange episode please help.?

He is a 15 year old Brittany Spaniel, hunted for the first 10 years of his life and has relaxed for the past five. I expected him to die quite a few years ago but, he keeps on kicking. He's never once had a seizure but just now he got up from sleeping. I called his name and he didn't respond, he got up and walked strait into the wall, literally he got up and headfirst into the wall in front of him. Now his eyes aren't opening at all, but they are responsive to feeling. (in other words his eyebrow twitches when i touch his head) I opened his eyelids and it looks like his eyes are in the back of his head like he's still sleeping. Today had been a record high of 113 degrees but he's always inside the AC for most of the day sleeping. I really have no idea what happened and would like an answer or two. I do understand that he is a 15 year old hunting dog and he might die any day.