When I'm dehdrated, I get this kaleidescope vision where the world is all sparkly and sort of pulsey and pixelated but in real life. The first time it happened, I was terrified it was the first sign of a migraine because I have friends who have them and described that "aura". But in my case, it seems to be a consistant thing associated only with dehydration and fixed pretty instantly with as much water as I can get. I take care to drink lots of water these days and haven't had a repeat in years.