I've done a few psychedelics in my day and I've noticed my vision is "looser" if you will. I can stare at things for a little while and sort of go back to the psychedelic state and see things move a tiny bit. Of course thats all there is, no body load or anything other than a slight movement. Its extremely minor and I sorta like it. I can't imagine bad cases of HPPD. I've heard of a guy who would see certain colors start to flash or melt or have hallucinations without being on any drug.