Here are a couple - um, three from my Aunt's email:
Focusing on the dot, move your head toward the screen, then back.
"To test this, stare at one spot for a couple seconds and everything will stop moving. Or look at the black center of each circle and it will stop moving. But move your eyes to the next black center and the previous will move after you take your eyes away from it.... ??
This one won't really work here...
Confusing....but thank God for brains!