The evolution of the eye comes up a lot in creationist literature as an example of so called, 'irreducible complexity' which claims that such a complex organ could not have evolved through intermediary steps, i.e., the intermediary steps would have no survival advantage. Clearly that isn't the case as this simplified cartoon shows. It's also easy to disprove yourself. Is there no value in less than perfect vision? Would you rather be totally blind or retain the ability to appreciate light and dark and general shapes (like patients who had cataracts removed a few decades ago)? Would simply being able to tell light from dark be preferable to total blindness? And so on.