How many times have we heard the old Darwinist canard that the human eye is “poorly designed”? As the argument goes, the vertebrate eye is poorly designed because our photoreceptor cells face away from the incoming light and the optic nerve extends over them, allegedly blocking some light. William Dembski and Sean McDowell’s new book Understanding Intelligent Design has an easily accessible and forceful rebuttal to this poorly designed Darwinist objection to ID, explaining that the design of the human eye is actually quite optimal:
The photoreceptors in the human eye are oriented away from incoming light and placed behind nerves through which light must pass before reaching the photoreceptors. Why?
A visual system needs three things: speed, sensitivity, and resolution. The inverse wiring does not affect speed. Nor does it affect resolution, except for a tiny blind spot in each eye. You don’t usually notice it because your brain’s visual harmonization system easily compensates for the blind spot. You need to do special exercises to discover it.
What about sensitivity? Sensitivity requires an inverted retina. Retinal cells require the most oxygen of any cells in the human body, so they need lots of blood. But blood cells absorb light. In fact, if blood cells invade the retinal cells, irreversible blindness may result.
By facing away from the light, retinal cells can be nourished by blood vessels that do not block the light. They can still be so sensitive that they respond to a single photon, the smallest unit of light.
(William Dembski & Sean McDowell, Understanding Intelligent Design: Everything You Need to Know in Plain Language, pg. 55 (Harvest House, 2008), emphasis in original.)
Dembski and McDowell also make the important observation that “no one has demonstrated how the eye’s function might be improved without diminishing its visual speed, sensitivity, and resolution.” (pg. 54) As it turns out, when engineers try to design better cameras, imaging devices, and bionic “eyes,” they use the human eye as a blueprint.
According to a recent MSNBC article, the supposedly poorly designed human eye is inspiring engineers: “Borrowing one of nature’s best designs, U.S. scientists have built an eye-shaped camera using standard sensor materials and say it could improve the performance of digital cameras and enhance imaging of the human body.” The article reports that the “digital camera that has the size, shape and layout of a human eye” because “the curved shape greatly improves the field of vision, bringing the whole picture into focus.”
And what about improving upon the human eye? The article reported that “[t]he device might even lead to the development of prosthetic devices including a bionic eye” as one scientist stated, “If you want to develop an eye to replace a human eye, certainly you want the shape to look like a human eye.” While inefficiently designed objects can still be designed (ever used Outlook, the current bane of my existence?), it seems very much like the human eye is not an inefficient or poor design.