Why the simplistic eyes?

What, if any, is the (presumably artistic) purpose in rendering the characters' eyes simply as black dots on a skin-coloured background in this movie, rather than as the usual, more-or-less naturalistic choice of black-pupil-in-colored-iris-in-white? Granted, there are some very nice stark light-and-shadow effects with reflective lenses (like Batman's mask and Gordon's glasses) here, and I suppose the otherwise understated eyes do emphasize those even more, but it looks decidedly odd in many facial close-up shots - once one notices it in the first place, at any rate.

I know that comics render eyes like that on occasion, but always perceived that as simply a lack of detail in panels in which facial features in general are too small and/or unimportant to warrant more intricacy. As opposed to a deliberate choice that would also be applied to facial close-up panels, that is.

Thoughts?

[Sample screenshot: http://image.bayimg.com/4f3d7c0187cd5fc2c2a702c942ae5d223ac1d1c7.jpg]