All opiates, not just oxycodone, at high enough doses can cause strange OEV/CEV, particularly as you nod. I've experience quite a lot of very odd, very realistic OEV while nodding- once I was lurking on bluelight (as you do while nodding) and I saw this little shadow man run across the screen, like running and jumping through the letters like it was some weird obstacle course. I don't think that it has any correlation with being close to going over though.
Apparently that's where the term 'pipe dreams' originated- it was a term for the strange OEV/CEV opium smokers have while nodding. But then again, William S Burroughs was often full of shit, great writer, full of shit.