No, they didn't mention it. The show was about morticians, and the guy talking mentioned that the dead man was going to be cremated with his favorite shirt, and then he mentioned that corpses could be cremated with almost anything, 'cept pacemakers. He didn't mention why pacemakers explode, I'd guess it's the battery.
As for glass eyes, they should probably just melt, but admittedly I've never stood around burning glass to see what'd happen.