That's awesome you noticed his eyes. Not many people did. Actually the thing that scared me the most about his character was how his left eye kept trying to stray. I thought it was a brilliant CG tactic, but I found out in an interview that the actor actually has a lazy eye and has trained certain eye muscles to keep it in place. During the filming, he said that every now and then he would just relax those muscles and let his eye slide to the side.
Amazing and SO creepy. It made it seem to me like something was trying to get out of the clown body. Or that his clown facade was slipping and the eye was the first indication. Loved it!!