This is a Maya scene I put together in version 2012.
Everything is neatly organized in a hierarchy of groups that allows you to move the controls/geometry. Everything is named clearly, unneeded history have been deleted. It is a fairly uncomplicated rig setup.. the iris open/close is a blendshape (liner) that is controlled by moving a simple slider control. The arch of the closing iris is preserved by a sculpt deformer inside the eye geometry.
The eyeGeo group can be constrained to your rig, and the geometry can also be smoothed, I left it as lo resolution as I could.
The textures are 2048x2048. Also included is the original Photoshop file so you can customize as you desire