Can you tell me more about hppd (hallucinogen persisting perception disorder)?

More on HPPD: There are a number of perceptual changes that can accompany hppd. Typical symptoms of the disorder include: halos or auras surrounding objects, trails following objects in motion, difficulty distinguishing between colors, apparent shifts in the hue of a given item, the illusion of movement in a static setting, air assuming a grainy or textured quality (visual snow or static, by popular description.