So I am not 100% confirmed with it, but have some symptoms I think either may be HPPD or something else. For starters the drug I used was the synthetic marijuana crap for about 6 months. Back in March of '15 I noticed I started feeling very numb in my whole body. My vision became strange. I wouldn't call it double-vision but I noticed I had some tunnel vision. What I see is hard to describe, but a few things has been if I look at where it's dark I can't see clearly, it looks as if I am looking through a dark void so to speak. When watching TV I can't really see peripherally. I have to look at the center to "see" it, if that makes any sense. If I see images side-by-side that messes me up. Also, when watching TV or videos online, if say, someone is talking, and they have an open window in the background when it's sunny outside the light looks EXTREMELY bright. Again, not sure if this could be HPPD or something else.