New Research Highlights Elegant Design in the Inverted Retina
Imagine sitting in an airport, waiting to board a plane. Thankfully you have something interesting to read as you wait for the flight. You glance up as someone walks by—it’s the pilot. To your dismay, you see he is wearing sunglasses and is escorted by a seeing-eye dog!
Some people claim this story is based on a real event. But of course, it’s just an urban myth.
The creation/evolution controversy is not immune to “urban myths.” Recent research has helped unravel one such “myth,” namely the belief that the vertebrate retina exhibits bad design.
In 1996, evolutionary biologist Richard Dawkins wrote in regards to the vertebrate retina,
Any engineer 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 backwards.1
The retina is a thin layer of light-responsive neural cells lining the interior back wall of the eye. It consists of photoreceptor cells that generate an electrical signal when light impinges upon them. At first glance the retina appears to be based on a questionable design. The light-sensitive region of photoreceptor cells orients away from the source of light. Furthermore, the nerve cell conduits to the optic nerve lie between the light source and photosensitive region of the photoreceptor cells—a design that would make any self-respecting engineer cringe.
Thus, vertebrates’ “backward-wired” retina became an exemplar of bad design. Evolutionary biologists like Dawkins consider faulty designs in biological systems as prima fascia evidence that life stems from undirected mechanistic processes, not from the activity of a Creator.
Debunking the myth
But further research into the construction and function of the vertebrate eye has unraveled the bad design myth. Most recently, a team of Israeli physicists performed modeling studies on the optical properties of radial glial cells. Their results confirm previous work by German scientists.2
In 2007, a team of German researchers demonstrated that radial glial cells associated with the retina act as optical fibers.3 That is, the radial glial cells (star-shaped cells that help maintain the structure of nervous tissue and transport nutrients to neurons) form fibers oriented in the direction of light propagation through the retina. This allows them to efficiently transmit light from the surface of the retina to the photoreceptors. Radial glial cells have a higher refractive index than the surrounding tissue matrix, serving as a low-scattering conduit for light, and thus transmitting images capably and with little distortion.
The work by the Israeli physicists supports the conclusion that these optical fibers compensate for the retina’s “bad design.”
In light of these new insights, it is easy to see that the inverted retina is a well-designed system, worthy of the Creator.
The Snopes.com website, devoted to debunking urban myths, has an entry for the “blind pilot,” but the last time I checked there was nothing about the vertebrate retina’s bad design. Looks like it’s time to update the site.
- Richard Dawkins, The Blind Watchmaker: Why The Evidence of Evolution Reveals a Universe without Design (New York: W.W. Norton, 1996), 93.
- A. M. Labin and E. N. Ribak, “Retinal Glial Cells Enhance Human Vision Acuity,” Physical Review Letters 104 (2010).
- Kristian Franze et al., “Müller Cells are Living Optical Fibers in the Vertebrate Retina,” Proceedings of the National Academy of Sciences, USA 104 (May 15, 2007): 8287–92.