I was very much thinking of doing one of these... Just didn't have a model handy, and didn't quite feel like searching for one just for this, so I did something else instead. I'm a big fan of eye pictures, though, and have done a number of them over time... Fun stuff!
6 - Very nice. Excellent 'DOF'. Criticism; undecided on the light reflections in the eye, even just one may have made this better, but I also tried to visualize it without any as well - not sure, but your call anyway. Color is very nice. Perhaps a slightly different angle or crop, incorporating the fore bottom lashes and possibly even the brow - or just to contradict that, a different angle eliminating the brow (if that makes sense), may have made this even better in my opinion, not sure. The very good use of a shallow DOF is what really makes this shot, so well done.
those are some lovely patterns in that iris. This person has the same combination of eye colors as me: brown interior, gold middle ring, green exterior. Eerie.