I had a wolf hybrid that would sleep with her eyes open if she was dreaming of running, her paws would flail around and she’d bark and growl. She was the most animated sleeping animal I’ve ever known. Once the dream ended her eyes would close again and she’d be still.
My dogs sleep with their eyes closed. But if you want to check if he’s awake just lean over and check his eyes for signs of recognition. If he doesn’t move his eyes towards (to look at you) you it’s possible that he is asleep.
Dogs have more than 1 pair of eyelids. I think if my dogs are sleeping with their eyes open they aren’t really in a deep sleep. Kind of day dreaming. But I don’t know I’m not a vet.