Carl Zimmer's two part post on the evolution and development of eyes is a must read:

Eyes, Part One: Opening Up the Russian Doll
Eyes, Part Two: Fleas, Fish, and the Careful Art of Deconstruction

Note that Carl points out that the fish Astyanax mexicanus has shifted toward phenotypic blindness via microevolution in 30 separate populations over the last 10,000 years in parallel fashion. This is not a tale that unfolds differently with every rewind....