An eye "very imperfect and simple"

The brittlestar has an entire carapace pitted with optically tuned calcite crystals.[1]

The photo is featured in a Darwin 'special' in Nature. The editorial says:

An even more likely development [in the next 50 years than the discovery of life beyond Earth] is that life will be created de novo here on Earth. The first experiments in whole-organism synthetic biology, such as the synthetic mycoplasma being worked on at the J. Craig Venter Institute in Rockville, Maryland, will cleave quite closely to the designs already developed by natural selection. But there are already schemes for going further — for using different genetic codes, for example. Although the synthesis of complex organisms might remain the stuff of fantasy for some time, new ways of building self-replicating, one-genome, one-cell organisms seem quite plausible. The development of creatures born from an idea, not an ancestor, will undoubtedly provide new insights into evolution, not least because the proclivities of such creatures to evolve will need to be kept in check.

[1] P.S. 28 Nov: There's a note on brittlestars by Mark H at Daily Kos