Raymond Moir and Michael McLelland burst into Alasdair Thorburn's flat in Perth.
Mr Thorburn told the High Court in Dundee he had returned to his flat from a pub and fell asleep. A short time later he was woken by two men in his flat.
Mr Thorburn, 68, said: "They tied my face with cling film or a broken plastic bag.
"It was tied round my mouth and up round my head. They were demanding my pin number – I eventually gave it to them."
They hit him in the face and put a cigarette out on it.
A jury found Moir, of Perth guilty of assaulting Mr Thorburn and robbing him.
Judge Lord Turnbull told Moir he faced a "substantial" jail term. McLelland is in jail over the attack.