The exciting thing is that we pretty much know how this effect comes about. Briefly, motion is a reconstructed quality, inferred from the timing of incoming light signals. Neural response latency is a function of contrast, so one can create apparent (illusory) motion by engaging the same motion perception mechanisms via suitably chosen contrast gradients.
Eye movements refresh the cascade.
Click here for the full screen version (worth it): http://www.moillusions.com/wp-content/uploads/2011/04/psychedelic-screen-melt.jpg