He that formed the eye, shall He not see? (Psalm 94:9)

The human eye is a very complex sensory organ with many parts working together to give us sight. The eyelids and lashes protect the eye from exposure to too much light, dust, dirt, bacteria, or other foreign objects. A film of tears, consisting of oil, water, and mucus is produced by the oil glands of the eyelids. These tears not only feed and lubricate the eye, they use enzymes to kill bacteria and nourish the surrounding tissue.

Like a state-of-the-art camera, the eye contains a self-adjusting aperture and an auto-focus system; but this is where the comparisons fail. The eye can adjust to a 10 billion-fold change in brightness in an instant as well as automatically enhance contrast.

Its colour-analysis system allows the eye to distinguish millions of shades of colour in extreme lighting conditions in micro-seconds.

The eye-brain combination produces a depth perception that engineers marvel at, particularly when they witness this system instantaneously calculate, for example, the exact force required for a tennis player to hit a top-spin back hand down the line with unnerving accuracy.

Light passes through the iris, the aperture, and then through the lens where the light is further focussed on to the retina at the back of the eye. This light-sensitive layer is thinner than a sheet of plastic wrap and is more sensitive to light than any man-made film. The best camera film can handle a ratio of 1000-to-1 photons in terms of light intensity. By comparison, human retinal cells can handle a ratio of 10 billion-to-1 over the dynamic range of light wavelengths of 380 to 750 nanometres. The human eye can sense as little as a single photon of light in the dark!

When photons of light strike the retina they interact with the photoreceptor cells and cause an electrical change and the release of neurotransmitters. Messages are passed through inter-connecting neurons within the retina. These retinal inter-neurons process the information and send the resulting nerve signals along the optic nerve to the brain. Each fibre of the optic nerve processes 100 “photos” each second. Each of those individual photos would be represented mathematically by 50,000 non-linear differential equations, all which need solving simultaneously to get a sharp image.

In addition to this, the brain has to be wired to interpret reversed and upside-down images and an overlap of sensory data, which allows for depth perception. How the brain is able to accomplish this feat remains entirely unknown.

If you have ever used a magnifying glass to focus light onto a paper to make it burn, then you know that the refractive power of a lens is dependent on its degree of curvature, which is inversely related to the distance it takes to bring the light together at a focal point. The higher the refractive power, the shorter the focal distance, and vice versa. The eye is dependent on the combined refractive power of the cornea and the lens (58 dioptres) to focus light onto the area of the retina for sharp vision. And as it turns out, the distance from the cornea to the retina (23 mm) is exactly what it should be to get the job done. An amazing “coincidence”!

Eye doctors know that about a four percent increase in the combined refractive power of the cornea and lens (or a lengthening of the eye) results in severe myopia (not being able to see the big E on the eye chart clearly). And a 25 percent decrease in both of these leads to difficulties with distance and near vision.

What is required for the system to work is for light to behave the way it does, for the eye to receive the light on the retina in just the right way, for the minute rods and cones to produce colour and definition, for the optic nerve to work as a signal transporter and for the brain to interpret the neurons in just the right way. If all these separate subsystems aren’t present and performing perfectly at the same instant, the eye won’t work and has no purpose. Logically, it would be impossible for random processes, operating through gradual mechanisms of natural selection and genetic mutation, to create 40 separate subsystems when they provide no advantage to the whole until the very last state of development and interrelation is reached.