The eye is often used by religious people and particularly creationists as an example of how something so intricate and complex can't possibly have come about by accident. Kirk Cameron used this example as his best argument when given 60 seconds to convince Atheists of a deity in this video:
For me it's clear that the reason Kirk thinks this is a compelling argument, comes from two major misunderstandings:
1: The misunderstanding of the evolutionary process
2: The misunderstanding of "Proof"
The misunderstanding of the evolutionary process is probably the most overarching cause of the inability to accept an Atheist viewpoint. I don't claim to be an expert; far from it; but I feel that I understand enough to be able to explain it to other people and to know that it is a viable scientific explanation of the origin of life and has been effectively proved by countless scientists and scientific data. This all makes it virtually impossible NOT to believe in it, and equally has impossible TO be able to believe in god!
Evolution is actually an unimaginably slow process stemming billions of years. The eye in fact evolved relatively quickly, just a matter of millions of years, compared to other biological systems. It began as a mutation of a similar receptor cell which gave that cell light-sensitive properties. Later, more cells of the same type clustered together to create a larger receptive field. After a few more hundreds of thousands of years the cells lined a small pit in the surface of an animal's body, allowing light to be detected from a wider angle and direction of the source of light to be determined. Then later again something resembling a crude lens grew over the pit to allow the eye to focus on near or far objects... You can see how these kinds of processes are cumulative and develop over their course. Kirk and Bill O'Reilly apparently can't, which is a major reason for why they are NOT Atheists.
Kirk's picture of a "Crocoduck" was possibly the most ridiculous thing I have ever seen used as an argument against evolution. Hopefully I don't need to tell you that ducks and crocodiles would have split apart in their evolutionary paths millions of years before either of them was called a "duck" or a "crocodile". There was however something that could have been called an "Apehuman" as some point millions of years ago. I think we called them Homoerectus.
The use of the word "Accident" is also a horrible example of just how little knowledge they both have of evolution. It's true that the evolutionary process contains "accidents" in the form of genetic mutation which create a characteristic (phenotype) that may be beneficial or harmful to the individual. Natural selection then sorts these out by killing off the ones with the harmful mutation and allowing the ones with the beneficial mutation to survive. The survivors go on to reproduce and pass on their genes to their offspring. Later down the generations, the same characteristic might mutate again into something more useful, and then we might call the end product... oh I don't know... an eye!
The misunderstanding of the word "Proof" has always been a problem when debating these kind of topics. Proof to a scientists means that the evidence FOR a theory has got to a point when it outweighs the evidence against by such a large amount, that it has become almost impossible to believe the evidence against. It is a matter of probability, and "Proof" would technically be a 0.999andafewmore9s chance of something being true, but to save time and simplify things, we simply say it is "Proven" or "True".
Many religious people say "Well god is true FOR ME" but it would be a misuse of the word "True" to say that. One can say "God seems more likely to me, given the evidence I have been presented" which would be a valid statement, although highly unlikely given that there is virtually NO evidence for a deity. Or one could say "I BELIEVE in God" which requires no evidence, but is unscientific and therefore, not particularly useful.