Haven't been here in a long time, just browsing and thought I would throw something out there that kind of comes up every now and then but should probably be elaborated on some more.
At least in my case, I also had vestibular issues along with HPPD. It comes up on here every now and then from someone and I'm pretty sure David has said HPPD people show vestibular dysfunction, not that I'm trying to use him to advocate a point I'm just pretty sure without going and looking back, shit it even says it in wikipedia. I had to go through vestibular rehab awhile back and I figured I might elaborate so that it might help somebody else, it could probably help some people with orientation and possibly reduce trailing phenomenon. An easy way to kind of tell if you've got something going in that area is to stare at an object, a point, something small say like a neon timer on a oven clock, or something that just sticks out like that. Stand about six feet away from it and shake your head back in forth slightly fast, not quite as fast you can and see if the object "trails" or blurs more to one side or both more than you remember it use to, kind of like when a kid is saying NO when they're shaking their head assertively, that speed. If it does, then it's probably there. The constant illusion of movement disorganizes your properception or sense of where you are in space and so on, anyway, there is a way to fix this or in the least greatly improve this aspect.
To save you the trouble of having to set up with on these rehab guys(mine was a real douche and a fucking prick, just sayin), and going through the doctor and maybe embarrassing yourself, have someone give you the blank stare, or feel like your begging for some dickhead doc's mercy, this is what they're going to ask you to do(after about $2000+ btw). : )
So when I went through the guy basically had a WHITE business card, so you'll need something that size, You'll also need a black marker/sharpie/or just a black pen with some ink, some tape, and a blank White background, preferably a wall.
Here's what you do, just follow what I'm saying, it'll come together. Draw an uppercase Z on the blank side of the business card. You need to make this the full size of the business card meaning write the Z long way on the card. The horizontal lines of the Z go to the ends of the card and the diagonal line goes across the longer height of the card. You basically make it big enough to cover the whole fucking card, trust me you'll see it.
This is best done with a black sharpie, it needs to be about that thick, black, don't ask me why, that's just what I had.
Next, on the Z, you put a black line horizontally in the middle of the Z about half the length of the top and bottom horizontal lines, so it's like a - with a Z superimposed on it. Don't ask me why, that's just what it was.
After that, you will need the tape, scotch tape works fine, any tape really. Tape the other side of the card and place the card at EYE LEVEL against a BLANK WHITE WALL/BACKGROUND, make sure everything lines up straight.
Once you've done this, you stand about six feet or so away from that background. Once there, you simply shake your head back and forth fast enough that it blurs just a little bit, don't do it as hard as you can at first. Make sure, you are completely turning your whole head, you will probably have a tendency to just want to maybe move your chin back and forth instead of your whole head so try to make note of it, you'll see what i'm saying. Do this for about thirty seconds or so and once the thirty seconds are up, stop shaking your head and stare at the Z for about thirty seconds, you will feel a little dizzy, try to concentrate while you do all of this. You should notice that when your shaking your head back and forth that the little blurs of the Z start to dissappear, it's hard to explain, it's like that bad information gets taken out, you'll see this rather soon and you'll know what i'm talking about.
Give yourself a couple of minute and repeats the exercise about five times. Do this three times a day, you will notice that the "blurs" start to disappear and are not as pronounced when you begin the exercises after awhile.
Do that for a couple of weeks and see where your at.
Some asshole charged me over $2000 for that and they were real dickheads, so fuck them, everybody can get it for free. I looked online and had a hard time finding that so I guess it's under lock and key. Hahahaahha
There's also variations of that exercise, You can stand further away and walk towards the Z, and walk backwards, that's enough for now, you should really give it a try. People do this after car accidents, concussions, ect after their vestibular system gets out of wack. I don't think it will be a cure all, but it should help in some aspects for some, and every little bit helps.
There was also another exercise where they wrote an A on a business card and asked me to hold in my hand at arms length and move it back in forth in my hand while moving my head in the opposite direction but i never really followed through with that one(being a dumbass), the dude really pissed me off, real dickhead, I'm sure it would help, hopefully now someone else doesn't have to deal with that ever.
The doc that sent me that way was a Neuro Ophthalmologist. The test I took that I failed that sent me there was a Videonystygmagraphy, and a caloric test, where they blow hot and cold air in your ear and record your reaction. It was crazy when they blew the air in my ear, I felt like I was falling through a tornado, everything was spinning, but it's just for a couple of seconds. Since all you dudes are seeing these doctors, you might want to ask for one, an ENT, and primary can probably get you one too. My asshole doc never even gave me the results, asked for them, never saw them, just sent me to rehab, I guess I'd probably be a detached asshole too if I saw all these people all day with brain problems that I could only do so much for. Anyway, I hope somebody gets some help from this! : ) Provide some feedback if you do and maybe it should get tagged.