I've been actively experiencing symptoms of HPPD since I quit abusing DPH more than six months ago now. I used DPH regularly in very high doses, several times a week for about a month. All symptoms I had while using I just dismissed as "hangovers" at the time and it's not until recently that I have been able to acknowledge to myself that some, if not all, of what I'm experiencing is HPPD.
I'll start with the most prevalent symptom for me: color confusion and troubles with color discrimination. Sometimes I'll be looking at a whiteboard in class and it'll start turning yellow and blue, etc for no obvious reason. I'll look away and then look back and it'll be white again. Colors right next to each other I can sometimes have trouble telling the difference between. For example sometimes I can look at a green and blue checkered pattern and I'll only see all green or all blue, though I can tell there is a pattern somehow. It's kind of hard to explain.
My next most frequent symptom is my problems with light and dark. Prior to my deliriant use I could see very well in the dark and bright things didn't continuously bother my eyes. It's almost as if my eyes won't "adjust to the dark" so to speak. Even the things I can see in limited light just look like blobs to me. Likewise bright things in dark environments bother my eyes. I have difficulty using my laptop and watching the television in complete darkness. It's not the kind of ouch, painful, wince kind of difficulty, it's just annoying and seems to make my ability to see things even just feet away difficult. Similar to this I see the "starburst" effect on every set of headlights and every streetlight I ever come across. No matter how much I stare at it trying to make it go away, it just won't.
I also have difficulty focusing on text sometimes. It will just blur together and I can stare at it for minutes upon minutes and still not be able to comprehend a word. Somewhat similar to this, anything and everything with a "random" or abstract pattern I can find things that aren't actually in the design. If I stare at a pattern for too long I'll find faces, objects, and words. Then if I look away and try to find it again a few seconds later I often cannot.
Perhaps the most frightening "symptom" of all of this is an intense feeling of depersonalization. I have periods of time where I feel virtually nothing at all. I often get this feeling when alone, so I've minimized it some by forcing myself into social situations but there are times even when I'm with friends that I don't feel like I'm there at all. It's a terrible feeling and I don't remember feeling like his at all before my experience with DPH. I hate to associate this with HPPD; this could simply just be an effect of DPH, or perhaps I've always had these problems with depersonalization previous to this and the HPPD just increased the effects. I'm not sure, and I'm not sure if I'll ever really know.
All in all, I have to say I hate HPPD. I've heard people who don't experience HPPD complain that they "wish they could experience something like that", but I wish they would understand that it feels horrible. There are days when I don't notice my symptoms as much as other days, and I think I'm growing used to the symptoms if that's even possible. I don't feel like they are going away at all, but that my body is finding ways to become used to the symptoms. I despise it. I'm terrified one day I'm just going to snap and go absolutely insane. I regret absolutely nothing in my life aside from my use of DPH, but I regret that shit like hell. I feel like I've completely lost control over aspects of my life due to some stupid drug I thought would be a cure for boredom.