A million years ago when i was working at a studio in NYC, I decided to test the limits of a Phase One P45 back (when this was the newest technology). I found these photos and thought it would be fun to share.
I used a Hasselbad 555 body with an 80mm lens and 2x extension tube. I put a single head with a reflector camera right, put my subjects within a couple inches of the lens, blasted a flashlight in their eyes to close the pupil and brought this landscape to the screen.
Light eyes like mine didn't have the same depth and detail as the darker tones.
Eyes are as individual as fingerprints. Each example is a different friend. In Aron's eye above, you can see his long eye lashes reflecting back.
These images are cropped in but the P45 digital back could easily handle it.