I would like to approach this question by asking a couple of questions myself. Why would an evolutionist think that evolution would develop a design that is suboptimal? This is the same evolution that claims responsibility for the origin of all of the remarkable mechanations of the cell, and for the functioning of the human brain. How can an evolutionist, who will come up with a ready explanation for each new functionality of the eye as it is discovered, use what appears to be a limited understanding of the structure of the eye to argue against a Creator? This does not make sense to me. But lets begin by looking at what evolutionists have said about the human eye. Dawkins has stated:
"Any engineer would naturally assume that the photocells [of the optical device, or eye] 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. This means that the light, instead of being granted an unrestricted passage to the photocells, has to pass through a forest of connecting wires, presumably suffering at least some attenuation and distortion (actually probably not much but, still, it is the principle of the thing that would offend any tidy-minded engineer!)." (Dawkins R., "The Blind Watchmaker," 1991, reprint, p93).
The influential neo-Darwinian theoretician George C. Williams has stated that the vertebrate eye is "stupidly designed" ("Natural Selection: Domains, Levels, and Challenges," 1992, pp72-73), using similar reasoning, and anthropologist Jared Diamond claims that "A camera designer who committed such a blunder would be fired immediately." ("Voyage of the Overloaded Ark," Discover, June 1985, pp82-92).
But all of this discussion is predicated upon an assumption that the vertebrate eye is not optimal, an assertion that has never been documented. In fact, in the quote from Dawkins cited above, he himself admits such by suggesting light is "presumably suffering some attenuation", and then confessing "(actually probably not much...)", here hedging, because he knows that the human eye is capable of detecting a single photon of light under optimal conditions, a feat that is nothing short of a spectacular demonstration of optimization. This subject has been covered in some detail in an article by George Ayiob.
The vertebrate eye is designed in such a fashion that light entering the eye must transit several layers of cells before reaching the photoreceptor cells. This may result in some attenuation of visual acuity. An additional concern about the design of the vertebrate eye has to do with the "blind spot" This phenomenon results from the coalescing of the nerve fibers above the retina into the optic nerve, that dives through the retina at that spot. Since there are no photoreceptors there, a blind spot results. The invertebrate eye, such as that found in the octopus, is arranged in the opposite order. The photoreceptor cells are encountered first, and the nerve cells are below them. There is no blind spot.
Which design is best? This is not an easy question to answer. In the vertebrate eye, the photoreceptor cells lie in contact with the opaque pigment epithelium. This tissue prevents the transmission of light past the eye, and also is involved in the critical process of recycling exposed photopigments, a critical process for eyes of animals that are very active, since it allows for tight packing of photoreceptor cells and rapid recycling of used photopigments. The invertebrate eye, that lacks this feature, may have to sacrifice the ability to keep up a sustained high level of visual acuity for the possible gain in visual acuity, but this is only speculation. In any case it is far premature to conclude that one design or the other is inferior without having physiological bases for such statements.
As research on the functionality of the eye continues, we learn more of its fantastic ability to receive and process signals. The more we learn, the more we are convinced that no plausible mechanism in evolution can produce such a structure with the properties it possesses. This trend, and past experience assure us that when we have a fuller knowledge of the functional properties of the vertebrate eye, we will understand why the retina is designed the way it is. Recent developments along this line include an article in Nature by M.J. Berry II, I.H.Brivanlou , T.A. Jordan and M. Meister, entitled "Anticipation of moving stimuli by the retina," (398:334-338). In this article the authors explore one of the most phenomenal feats of optical response ever discovered: the ability to precisely anticipate the position of a moving object at the level of the retina. Gegenfurtner, in an article in the same issue ("Neurobiology: The eyes have it!" 398), summarizing the paper by Berry, et.al, states:
"In a stunning surprise, Berry et al. now show that motion anticipation not only starts at the retina, the first stage of processing in the visual system, but that it also follows from current models of retinal processing. The basic ingredients are all well studied and common to many stages of processing in the visual system. So how do these ingredients work to produce motion anticipation? The most important part of the process is actually the simplest -namely that retinal ganglion cells pool their inputs over large regions of the visual scene (their receptive fields)." (p291).
This amazing new understanding of how the "backward" retina can perform calculations of a very high order is no deterrent to evolutionists, who quickly integrate evolution into our understanding of the process. To explain the existence of this phenomenal ability in the retina, Gegenfurtner suggests:
Issac Newton was also impressed with the design of the eye. He wrote:
"Did blind chance know that there was light and what was its refraction, and fit the eyes of all creatures after the most curious manner to make use of it? These and suchlike considerations always have and ever will prevail with mankind to believe that there is a Being who made all things and has all things in His power, and who is therefore to be feared... We are, therefore, to acknowledge one God, infinite, eternal, omnipresent (always everywhere), omniscient (knowing all things), omnipotent (all powerful), the Creator of all things, most wise, most just, most good, most holy. We must love Him, fear Him, honor Him, trust in Him, pray to Him, give Him thanks, praise Him, hallow His name, obey His commandments, and set times apart for His service, as we are directed in the Third and Fourth Commandments, for this is the love of God that we keep His commandments, and His commandments are not grievous (1 John 5:3). -Sir Isaac Newton; from his Philosophy on Nature: Selections from His Writings, H.S. Thayer, ed. (New York: Hafner Pub. Company, 1953).
2010 Arthur V. Chadwick, Ph.D.