One of the arguments against the idea of an intelligent designer, going back at least to David Hume, is that if such a designer exists it must be incompetent given all the "bad" designs found in nature. One of the prized exhibits in this argument has for years been the "backwards" design of the retina, but, unfortunately for many authors who've hitched their Darwinian wagon to it, this old horse appears headed for the glue factory.
An article in New Scientist explains why:
It looks wrong, but the strange, "backwards" structure of the vertebrate retina actually improves vision. Certain cells act as optical fibres, and rather than being just a workaround to make up for the eye's peculiarities, they help filter and focus light, making images clearer and keeping colours sharp.
Although rods and cones are responsible for capturing light, they are in a curious position. Hidden at the base of the retina, they are covered by several layers of cells as well as the bed of nerves that carries visual information to the brain. One result is a blind spot in our visual field, leading the vertebrate retina to be listed among evolution's biggest "mistakes".
Light clearly gets through, however, and in 2007 researchers analysing the retinas of guinea pigs reported that the glial cells which nourish and physically support the bed of neurons also act as optical fibres for the rods and cones. These M�ller cells are funnel-shaped, with wide tops that cover the surface of the retina and a long slender body that guides light to the receptors below.
Now Amichai Labin and Erez Ribak of the Technion-Israel Institute of Technology in Haifa have used data from human eye cells to model the workings of the retina. Their findings suggest that sending light via the M�ller cells offers several advantages.
The rest of the article gives a very interesting explanation of the two advantages these researchers have discovered. Besides these there are other excellent reasons for wiring the retina the way it is that have been understood for some time and which are discussed in this article.
One might think that theists would be heartened by such findings since they seem to support the idea that a designer played some role in the creation. Not so Ken Miller, however. Miller is a theistic evolutionist whose career is heavily invested in persuading people that there's absolutely no evidence for intelligent design in biology, particularly in the human eye, and he's adamant that we not draw any inferences from the research cited by New Scientist that would support ID:
However, Kenneth Miller, a biologist at Brown University in Providence, Rhode Island cautions that this doesn't mean that the backwards retina itself helps us to see. Rather, it emphasises the extent to which evolution has coped with the flawed layout. "The shape, orientation and structure of the M�ller cells help the retina to overcome one of the principal shortcomings of its inside-out wiring," says Miller.
Well, this is certainly an odd take on the research. One might think that the backwards wiring of the retina is only backwards if it impedes vision, but this system actually aids vision. Nevertheless, Miller assumes it's still backwards, apparently because it's not how he would have designed it, and then marvels at how evolution has compensated for the engineering error.
I think probably the retina is less backwards than is Miller's reasoning. If Professor Miller wants my advice it would be to stop digging, throw down his shovel, and pretend that he never heard of the retina.RLC