TopHat
I know what you're talking about.
I can do the same thing.
It hurts my eyes after a while, but I don't get migraines.
It just helps me concentrate if a lot is going on around me.
I do it at school a lot.
It almost seems like something is being pushed from the back to the front of the eyes to blur it.
No real idea though.
@Everyone talking about squinting. It isn't squinting.
EDIT:
http://www.medhelp.org/posts/Eye-Car...es/show/495079
LINK FOR GREAT JUSTICE!