The first instance of HPPD ever was discovered in 1987 when a college freshman took a small amount of LSD on the way to a party. He described his trip as mild, and said the effects had pretty much worn off by the time he got back to his dorm. However, the next morning when he woke up and opened his eyes, he was alarmed to find that some of the LSD effects still remained. Throughout his day, he noticed light became streaked, and he could see beams even as he looked away from it. Afterimages of texts lingered in the air after he looked away from his textbooks. When he turned the page, a long cascading series of replica pages trailed behind. This persisted for days, and the student became more and more panicked. He went to psychologists, which had no idea what it was. His parents were even less help. Finally, he broke down, dropping out of school and entering rehab. A diagnosis was not found for him. He did not have any underlying medical condition, and the drug had not been laced. Years went by, and the trip continued on.
HPPD is a chronic and debilitating condition. Sufferers know what they are seeing is not real. Their surroundings appear blurred by afterimages (palinopsia) and trails (akinetopsia). They view sparkles and flashes of bright light. Blobs of color float around the air, heads appeared magnified or shrunk, and halos appear around peoples heads. Eventually, suffers become dissociated and disconnected from the world. They become depersonalized and depressed. Up to 65% experience chronic panic attacks, and 50% depression. Some patients believe their only escape is suicide.
Unfortunately, there are very limited treatment options and no cure. Sufferers can take benzodiazepines and anti-epileptics. They can also see a therapist. In some cases, sunglasses seemed to make them feel more comfortable.
Here's a link to a video on Youtube which is a simulation of HPPD.