Here's a subtle hint. Masking, Blend Modes, more than one layer in the project, a source for the black goo, and tracking.
You track the shot, apply the track to a mask layer to isolate the eyeball, then create the flowing black goo with a fractal, or a particle system, or by simply filming ink in water. Scale size track and blend to taste.
Figure out how to do it in Photoshop and then "the technique apply to After Effects you will."
