I've done a lot of reading up on it. Some people may have it without any drug use. And like I said, I can't say that my drug use caused my symptoms....although I'm positive they didn't help. To elaborate, I've done acid six times....five were which after I determined I had hppd...and my eyesight had remained the same. I've been having terrible anxiety lately but I've been sober for mo.ths now and have made dietary changes as well, in an attempt to be healthier overall. It's just frustrating that everything is constantly moving around me, that's the worst for me. The visual snow and things shaking...nothing ever looks right. It's a wonder I've not gone totally mad.