The beautiful complexity of the human eye
The human eye is brilliantly complicated, made up of a superb, interconnected system of approximately 40 individual subsystems. These include the iris, pupil, retina, cornea, lens, and optic nerve. By simultaneously detecting contrast while also capturing faint details, the human eye exhibits superiority over the most sophisticated camera today. Its design has been maximized for life in our environment.
The retina, the innermost, light-sensitive layer of eye tissue, can be thought of as equivalent to the film in a camera, or as a sensor with cells that act like individual pixels in a digital display.
The primary light-sensors in the retina are the photoreceptor cells. These are of two types: rods and cones. The rod cells are highly sensitive and are optimized for low-light, black-and-white vision. There are approximately 90 million rod cells in the human eye spread across the retina. Cone cells, on the other hand, are less sensitive and require bright light to function; they provide colour vision.
There are approximately six to seven million cone cells. All of them are concentrated near the macula, the oval-shaped pigmented area in the centre of the retina. Additionally, there are three varieties of cone cells that are sensitive to different colours of light. Between them, they span the visual range of wavelengths of the electromagnetic spectrum (400–700 nm):
- L-cones (long-wavelength) are sensitive primarily to red in the visible spectrum
- M-cones (medium- ) are sensitive to green
- S-cones (short- ) are sensitive to blue.1
The retinal photoreceptor cells translate the light impressions they receive to electric pulses. These are sent to the brain via the optic nerve. The visual cortex, the part of the brain that processes visual information, interprets the pulses as colour, contrast, depth, and other information. (There is also a lot of data processing in the retina itself.) This allows us to make sense of all the data, and ‘see’. We can discern about 10 million colours (but see box ‘Extra colour vision?’ below).
The eye, optic nerve, and visual cortex are separate and distinct subsystems. Together, though, they capture, deliver, and interpret up to 1.5 million pulse messages per millisecond. To even approach the performance of this incredible task would take dozens of supercomputers, programmed perfectly and operating flawlessly and concurrently.2
Bad design?
Despite these incredible characteristics, many evolutionists have claimed that the retina in vertebrates, including humans, is poorly designed and suboptimal.3 Arguing against the idea that the eye was intelligently designed, they refer to our retina as inverted (i.e. the ‘wrong way round’). This is because the light-sensing (photoreceptor) cells are oriented so that their sensory ends are directed away from incoming light. Richard Dawkins, an atheistic evolutionary biologist, author, and speaker, claims that the problem is that “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.”4
Additionally, evolutionists maintain that at the point where this wiring over the retinal surface passes through the retina to the optic nerve, a ‘blind spot’ is produced that no intelligent designer would have wanted.
The opposite arrangement, commonly seen in invertebrates (animals lacking a backbone, such as the squid), is termed verted, implying that it is the ‘right way around’, because the light-sensing cells face the incoming light, and there is no ‘wiring’ in front of them. Many evolutionists have claimed this orientation is more efficient, and ridiculed the inverted layout.
However, this entire line of argument could have been regarded as suspect from the outset. Consider for example the brilliant capabilities of the eye of a hawk (fig. 2) or eagle, compared to our own already superb vision. The expressions ‘hawk-eyed’ and ‘eagle-eyed’ are well justified. The eye of a hawk lets it see small prey from a great height before diving down at lightning speed. It is four to five times better able to see objects at a distance than we can. And its visual acuity (sharpness) is about eight times better than our own. Yet its eye is also the allegedly inferior ‘inverted’ type! Squid just don’t see as well. In reality, a squid eye is a compound eye with a single lens, not just the reverse of a vertebrate eye.
Small wonder that the ‘inverted’ argument for the alleged inferiority of the vertebrate retina has been soundly scientifically refuted, with multiple lines of evidence showing that it is in fact optimal for its environment. There are sound design reasons behind the arrangement, as articles on creation.com explain.5,6,7 And Dawkins’ supposedly superior arrangement would require blood vessels in front of the retina, blocking out most light.8
In addition, one component of the retina’s “forest of connecting wires” Dawkins mockingly refers to are the so-called ‘horizontal (nerve) cells’. Studies have shown that they are part of a complex feedback system that actually improves contrast and sharpens edges without sacrificing shadow detail.9 As a result, compared to a camera, the human eye is far better at capturing contrast while simultaneously detecting faint details (fig. 1).
Our eye’s design has indeed been optimized for life in our environment and would undoubtedly function poorly in another. Additionally, it has been determined that the ‘blind spot’ does not even slightly interfere with vision efficiency.5
Optimized for purpose
Optimization means “the act, process, or methodology of making something (such as a design, system, or decision) as fully perfect, functional, or effective as possible.”10 Undoubtedly, the design of the human eye satisfies this definition. Contrary to evolutionary thought, the human eye, with its precise design, splendour, beauty, and perfection affirms an intelligent Designer.
As Psalm 111:2–3 declares,
Great are the works of the Lord, studied by all who delight in them. Full of splendor and majesty is his work, and his righteousness endures forever.
Extra colour vision?
It is believed that up to 12% of women are ‘tetrachromate’, in having a fourth (orange) type of cone cell perception.1 This is thought to be from an inherited mutation in the visual pigment used in one of the cone cell types. However, this mostly makes no difference to how the individual perceives colour in practice. This is probably because she still only has three colour ‘channels’ for interpreting signals from the eyes.
Rarely, though, there are individuals with this condition who are able to perceive many times more shades of colour than most. Whether this is an advantage or distraction in practice is not clear. One lady described that she saw dull grey as “oranges, yellows, greens, blues, and pinks.” 2
References and notes
- Mukamai, R., How humans see in color, American Academy of Opththalmology, 8 Jun 2017; aao.org, accessed 11 Sep 2022.
- Tetrachromacy (‘super vision’), healthline.com, last medical review 13 May 2022.
References and notes
- Human visual response, section 6.2 in Olsen, R., Remote Sensing from Air and Space, 2nd Edn., Spie Press, Bellingham, WA, pp. 120–121, 2016. Return to text.
- Richards, L., It couldn’t just happen: knowing the truth about God’s awesome creation, Thomas Nelson, Nashville, pp. 139–140, 2011. Return to text.
- Wieland, C., Seeing back to front, Creation 18(2):38–40, 1996; creation.com/seeing. Return to text.
- Dawkins, R., The blind watchmaker, W. W. Norton, New York, 1986. Return to text.
- Gurney, P., Is our ‘inverted’ retina really ‘bad design’? J. Creation 13(1):37–44, 1999; creation.com/retina. Return to text.
- Sarfati, J., Backwardly wired retina “an optimal structure”: New eye discovery further demolishes Dawkins, creation.com/mueller-v-dawkins, 27 May 2010. See bottom of article for refutation of P.Z. Myers’ critique. Return to text.
- Sarfati, J., Fine tuning of ‘backward’ eye is vital for colour vision, Creation 38(1):17, 2016; creation.com/eye-optimization. Return to text.
- Marshall, G. (ophthalmologist interviewee), An eye for creation, Creation 18(4):19–21, 1996; creation.com/marshall. Return to text.
- Jackman, S., and 4 others, A positive feedback synapse from retinal horizontal cells to cone photoreceptors. PLOS Biology 9(5):e1001057, 2011. Return to text.
- Merriam-Webster’s Collegiate Dictionary, 11th edn., Merriam-Webster, Springfield, MA, 2003. Return to text.
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