Effects --> Generate --> Circle, Mask and shape layer keyframes, whatever. You seriously need to read the help.
A bunch of copies of a shape layer animated by hand to fill the screen, pre-composed and used as a track matte. CC Particle World with a textured disk as a particle used as a track matte. CC Ball Action as a a track matte. Shape layers with repeaters as a track matte. There are hundreds of possibilities if you just take the time to learn some of the fundamentals.
This is nothing more than setting up your animation and using that animation as a matte source to reveal the eye layer. It's really basic stuff.
Thanks Mylenium, I will.
Thanks Rick, I will keep learning as much I can and keep up with it.