I do not think you did any long term damage but 80mg is extremely potent and one of those could have caused an accidental overdose...The first timeI took Oxy it was 60mg and I threw up for two days; that was even with a tolerance to 2-3 Percocet 10/325. That should have been my warning. Glad you stopped, never take them again!
By the way, OxyContin IS synthetic heroin. All opiates and opioids convert to morphine in metabolizing them. The difference, for the most part, is that Oxy is a more consistent, factory and FDA regulated, pure form of the same drug, a morphine metabolite.
The chemical make up of opiates fit right into the "opiate receptors," of the brain so well, our bodies don't see it as very toxic. It takes high dose for a long time to actually cause permanent damage with opiates. Pure heroin is not even real toxic to the body or brain, it is the impurities, not the opiates that cause damage, mostly. Unless there is some pre-existing condition that the opiates triggered, there really is no scientific reason you would have done permanent damage with pharmaceutical grade opiates. Just my opinion, of coarse.
I'm not a doctor,but I think you'd be fine.