Photographer Suren Manvelyan has produced an amazing collection of photographs of eyes over the last couple of years. He started with a phenomenal set of images from human eyes and has now expanded his collections to include 3 sets of animal eyes. Part 1, Part 2 and now Part 3.
Spending some time looking through them is a good investment, particularly if you consider the evolution that has shaped the biology as looking at the different structures of the outer eyes gives you clues as to the environments these organisms live in.