With my light ray bias at .01 inch, even more of the iris is in shadow now. Only the very edge is lit.

If I increase the light's ray bias to be larger than the distance from cornea to pupil, then it would light the whole iris. But that would cause other problems.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)