know exaclt what you mean. i get it all the time though even when i dont get up fast i get it for about 5 seconds
looks like stars in the night sky
cant see a single thing except for the back backround with, shiny or coloured star looking spots.
you get the exact same thing when your about to faint, you get it for about 20 seconds, and it scares you and you realise it doesnt fade to normal, if that happeneds lay straight down on the floor, it will take around 5-10 seconds and youll see again, youll feel dizzy so go straight to bed, untill you feel better
if your at school or work or in the public, sit down. and go straight