Sorry but that's bullshit.
For Beowulf Sony Imageworks had electrodes measuring eye movement from the muscles, and even there they keyframe animated the eyes in more then half the movie.
There's no way to reliably capture eye movement, period.
You're probably right. I've seen a bunch of making of features of Heavenly Sword where I thought the actors were wearing contact lenses with tiny little white balls on them, like here:
But I may be mistaken, it's probably a trick of the light and the rest is just attached to their eyelids only. Still the amount of 'balls' used for the face don't seem to be anything like what they used in Uncharted though.