Miss Nancy - your avatar has grown!
Exactly - it also has different hues - not just a blank red dot which will look cartoonish. I'm afraid that if it is made a "material" how much gets lighted/you will see will depend entirely on the lighting (unless the Materials Lab has a Luminance Channel - I'm blanking).

The closer a flash is to the lens, the more reflection you will get from the retina - which is why we only see it through the pupil.

I'm still thinking your best bet is postwork if you want it to look real - and years of family and friends' photos would be an almost endless supply.