You describe that sensation very well (and I agree with you, I don't think it's related to anxiety), and I WANT a nice explanation like the eyesight thing, but when this has happened to me, about half the time it starts when I'm lying in bed with my eyes closed. So ??? (Also, sounds feel fast as well, not just movements). That's interesting that with you it correlated with video games, but it doesn't now that you're an adult. Very mystifying. And I totally know what you mean about the "brain change" before it really ramps up.
I love hearing about everyone's experiences with this. The more people that comment here, the more curious I get because it means this is happening for some actual reason, and isn't just a random freak occurrence.

OH and on the thyroid note: I've had my thyroid hormones checked many many MANY times, and they're always steady and normal. So the thyroid cause, at least for me, is out.