Considering our eyes are wired inside-out (the nerve cables are on the same side light comes in, so they have to go through a hole in our eye, the blind-spot), I'd say that natural selection gets stuck in local optimums all the time. Cephalopods like octopuses have very similar eyes to us, but they evolved completely separately and their nerves are wired in "the right way".
So in our case the starting conditions just lined up the way it did and no single step (or series of steps) easily flipped our wiring, so we just rolled with it (and we get by quite well).
So in our case the starting conditions just lined up the way it did and no single step (or series of steps) easily flipped our wiring, so we just rolled with it (and we get by quite well).