Even Darwin was fascinated by vision and said he got chills when he thought about how perfectly the eye was constructed. The eye is covered by the cornea, which consists partly of collagen. Everywhere else in the body, collagen is opaque, but in the cornea, it is transparent. The lens is a masterpiece that bends light in precisely the right way to form a sharp image on the retina.
I will briefly describe the biochemistry of vision to illustrate its complexity. When light enters the eye, numerous chemical reactions occur, beginning with the transformation of the chemical compound 11-cis-retinal in the retina into trans-retinal. This leads to the conversion of the protein rhodopsin into meta-rhodopsin II, which binds to the protein transducin. This complex then binds to guanosine triphosphate (GTP). As a result, sodium concentration decreases, triggering a nerve impulse that the brain interprets as a visual image. How a nerve impulse is converted into a visual perception is something that few truly understand. Vision requires all these substances to be present in the right amounts at the right time. It is nearly impossible to argue that such a complex, multi-step chemical reaction could have arisen by blind chance.
The retina consists of two types of light-sensitive photoreceptor cells: rod cells and cone cells. Each human eye contains approximately 125 million rod cells. These cells are highly sensitive, optimized for low light conditions, and responsible for black-and-white vision. Cone cells, on the other hand, are less sensitive and require stronger light to function. They provide us with color vision, and each eye contains about six to seven million of them.
The well-known atheist Richard Dawkins argued that the eye was poorly designed because the photoreceptors are located on the front side of the retina. He claimed that a smart engineer would have placed the sensors on the back instead. Since Dawkins was such a prominent figure, his criticism was often repeated. However, recent discoveries show that light is captured by Müller cells, which function like optical fibers, guiding the light to the photoreceptors in the most optimal way. Müller cells help filter and focus the light, enhancing image sharpness. So, Dawkins’ objection has been permanently refuted!
Dawkins, being a staunch evolutionist, argued that the eye developed gradually, claiming that an eye that is 5% developed would provide 5% vision. However, the reality is that the eye must be fully developed in order to function. Dawkins failed to distinguish between structure and function. There is only one accurate word to describe the eye and vision: genius!
I am also fascinated by the external muscles of the eye. Six muscles control eye movement—one moves the eye upward, one downward, one to the right, and one to the left. Two additional muscles are responsible for eye rotation. One of these, the superior oblique muscle, passes through a tendon loop attached near the nose. This muscle must be bent at an angle to enable proper rotation. It bends at exactly 54 degrees to allow the eye to rotate correctly. That is what we call engineering excellence!
From the book of prof emeritus Kjell J. Tveter “So much to wonder about”
