it's not that it's concave. look at the photos i posted again.  in each and every one, the darkest part of the iris is right under the highlight.  the lightest part of the iris is directly opposite it.  your texture with the burned in highlights and shadows shows the same effect, if more subtly.

your untextured eye does not show this shading.

everything i've seen so far shows a significant inset from the scelera.

every accomplished visual artist seems to use this effect to show depth to eyes.  from cartoonists and anime artists, to painters, to photographers. 

the only reason i keep saying anything is that not only have i personally had serious problems with irises that were too protruding, and not only have i witnessed this problem in galleries since i started using Poser, but "flat" or "dead" eyes are about third on the list of common criticisms i've seen, behind nostril glow and lack of shadows. 

in the end, it's not just about reality.  it's about what the renderer can do.  i'm not sure that a perfect scale model of the eye will actually shade properly in Poser or anything else.  in MikeJ's renders, the convex model with refraction looks way wrong, and the concave one with refraction looks right.  and i don't think i've ever been able to find a setting that got me realistic shading from the eyelid (though i have seen bagginsbill do this) and reflection from the lashes.  i've just about always had really strange reflections of the lacrimal back when i used D|S (many versions ago- no fresnel). 

but either way, it's ok.  i'd just rather not have to do the kind of work entirely repainting an eye  takes.  i think i was pretty good at it the last time i did, but it takes me a lot of painstaking work to do meet my own standards.  and since i'm looking forward to the finished Antonia becoming my new primary figure, i'd rather not personally find her default eyes unusable.  that said, i haven't been satisfied yet by what i can do with any figure's eyes.  kind of like their shoulders, knees and ankles.  since she's already ahead on the anatomy and joint issues, having better eyes would be icing, not the cake.