Has to be some type of composting -- optical or software. I don't see anyway to have decent focus on the eye itself and the reflection at the same time if it was a straight shot. Focus distance to the eye is very short -- maybe an couple inches max. the reflected image focus distance is the actual distance to the object reflected -- several feet to infinity. (Try this test, take camera and focus on your own reflection in a mirror, then without changing focus, shift sideways so the frame of the mirror is in view. It will be out of focus. Refocus on the mirror edge and your reflection goes out of focus.)
A flat mirror is the wrong comparison.
You really don't need CGI to have sharp eyes AND sharp reflections see the image below which is a simple proof. The image is made with an APS-C camera, HD video mode, f7.1 @60mm (EF-S Macro). @f/2.8 the same situation.
The cornea is a spherical mirror (in that case) and acts as a second optical element providing more or less sharp images.
The only problems are:
- avoid the reflection of the imaging system
- getting enough contrast (as you can see with my image with blue-gray eyes) - dark (e.g. brown) eyes are
much better but i have to live with what I have.
CGI is much cheaper and using a fisheye will give satisfactory distortions which are well accepted as reflections form the cornea.
So everyone is right - at least a little bit ...
EDIT: Forgotten the attachment - now available ...