I constantly have people misquoting Darwin on the evolution of the eye. I get countless people quoting me the following statement:
"To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree."
Unfortunately they are taking this quote out of its context. Now let's look at the quote in its entirety.
"To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree. Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection…"
It is quite possible for a complex organ such as the vertebrate eye to evolve step by step. In fact the vertebrate eye is actually wired backwards as Dawkins points in the following excerpt taken from page 93 of his book The Blind Watchmaker.
"Any engineer would naturally assume that the photocells would point towards the light, with their wires leading backwards towards the brain. He would laugh at any suggestion that the photocells might point away from the light, with their wires departing on the side nearest the light. Yet this is exactly what happens in all vertebrate retinas. Each photocell is, in effect, wired in backwards, with its wire sticking out on the side nearest the light. The wire has to travel over the surface of the retina, to a point where it dives through a hole in the retina (the so-called 'blind spot' to join the optic nerve."
If you don't believe your eye has a built in blind spot check the following picture and paragraph I got from: http://serendip.brynmawr.edu/bb/blindspot1.html
Close your left eye and stare at the cross mark in the diagram with your right eye. Off to the right you should be able to see the spot. Don't LOOK at it; just notice that it is there off to the right (if its not, move farther away from the computer screen; you should be able to see the dot if you're a couple of feet away). Now slowly move toward the computer screen. Keep looking at the cross mark while you move. At a particular distance (probably a foot or so), the spot will disappear (it will reappear again if you move even closer). The spot disappears because it falls on the optic nerve head, the hole in the photoreceptor sheet.
The other group of animals that has a camera like lens eye are the mollusks like the squids and octopus. Their eyes are wired the right way. If there is an intelligent designer why did he give mollusks a superior eye design? If you believe in the creation of the eye you should feel ripped off that you didn't get a state of the art eye. You got an eye that works well enough which is what you would expect from natural selection. Our first vertebrate ancestors had photoreceptors that had the nerve on the surface. Yes there is some distortion of light as it passes through the nerve but the ability to see far outweighed being blind. Animals that had more photoreceptors had better vision and could find more food and escape predators better than those that did not offering a huge selective advantage. The first mollusk eye was wired the right way to begin with so they do not have this flaw in their "design" as we do. Another interesting fact for you; vertebrate eyes are derived from nerve tissue where as the mollusk eye is derived from skin tissue. This really doesn't make a difference but it is another convincing piece of evidence that a complex structure like a camera lens eye evolved independently more than once.
The following text along with the video come from: http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html
When evolution skeptics want to attack Darwin's theory, they often point to the human eye. How could something so complex, they argue, have developed through random mutations and natural selection, even over millions of years?