I used my macro lens for this, with lots of natural light. In retrospect, I think I should have used manual focus, as it was pretty much impossible to get both eyes in focus at the same time on auto focus. You can check out the exif info if you like:)
Macro lens will sure make the details clearer but I've done this one with a macro filter and the macro setting on compact cameras will work as well.
I once tried with flash but it made all the iris detail blend plus making other parts of the eye really white, not to mention it turns one blind :D
Oh and I think the lighting helps a lot if it is strong but defused like sunlight so you wouldn't get the distracting reflections that I got.
I think I used the macro-function on my compact-camera.
These are the exif's:
Exposure: 0.025 sec (10/400)
Aperture: f/3.2
ISO Speed: 250
Focal Length: 8 mm
I hope this helps!
Exposure: 0.0333 sec (10/300)
Aperture: f/2.8
ISO Speed: 320
Focal Length: 4.8 mm
I once tried with flash but it made all the iris detail blend plus making other parts of the eye really white, not to mention it turns one blind :D
Oh and I think the lighting helps a lot if it is strong but defused like sunlight so you wouldn't get the distracting reflections that I got.