The Design

In Articles by Ronald L. DartLeave a Comment

Share with friends

I have to see my eye doctor three times a year, and I am always left waiting in his examination room. The walls there are covered with pictures and diagrams of the human eye. I often gaze at these pictures with something approaching religious awe. The eyes that I see all around the walls were designed. And surely no one could fail to see that.

It was one particular diagram that started me thinking. It was a simple vertical cross section of the eye with everything named. It was there to help the doctor explain things to his patients. The chart itself was designed to make things as simple as possible, so it was easy to pick out the different parts of the eye.

I already knew what rods and cones were. A navy school explained that to me so I would understand night vision. Rods and cones are the light sensors arranged around the back of the eye in the retina. There are millions of them in each eye. Light enters the eye through the cornea, passes through the lens, and is focused on the surface of the retina. When light strikes the rods and cones, a tiny electric current is generated. The current travels along fibers to the optic nerve, hence to the vision center in the brain, and we see.

It sounds simple enough. At least that’s what I thought until I noticed that there were 150 million rods and cones, and only 1 million fibers in the optic nerve. When we look at an object, an image is projected on the retina and stimulates all 150 million rods and cones. Each of them has to carry it’s own message to the brain so we can see the entire image that is projected there. Simple math tells me that 150 different signals have to travel down one optic nerve fiber. How is the traffic handled?

Having a basic knowledge of electronics, I knew that you could carry multiple messages down one wire, but those messages all have to be coded in such a way as to be properly directed and understood at the other end. I wondered how the coding was done.

I decided to ask my doctor when he finally came in. He thought for a minute and said, half joking, Well, there is this tiny computer chip behind the eye… We had a little laugh over it, and he went on with the examination. But I was not satisfied. I knew there was no computer chip, and I wanted to know how it was done. When I got home, I took my Britannica to my favorite chair, propped up my feet and started reading.

Much to my surprise, it turned out that my doctor was not joking after all. There really is a computer chip of sorts. It is not in the brain, where you might expect it to be. It is in the retina itself. The sensors of the eye, the rods and cones, are not hard wired into the brain. Behind the sensors is a network of interconnected nerve cells. I learned that groups of rods and cones are connected together in networks, and that the signals received by one influence the signals sent by another. Some signals are strong, and others are suppressed. The result is that the image we finally see is, in reality, computer enhanced.

If you look at a fine black line on a white piece of paper, the image of the line that strikes the retina is relatively broad and composed of shades of gray. This is because the optics of the eye are not geometrically perfect. In the nature of things, diffraction of light spoils the perfect image. The spread of light from the white areas into the black has to be corrected, so the tiny computer chip in the retina enhances the contrast. The rods that receive more light inhibit the rods that receive less, and the resulting transmission to the brain is a fine black line.

If you have ever played with lenses, you may have noticed a phenomenon called chromatic aberration. It is in the nature of a lens that it focuses different colors of light at different lengths. The result is a margin of colors around the image created by the lens. As you look at a white object against a black background, the lens in your eye created just such a halo of color around the image on your retina. But you do not see it, because the little computer chip in the back of your eye suppresses it. The Designer wanted you to have a nice clean image to consider.

But that is not all the little computer does. Take the problem of panning, for instance. We know that if we take a movie or video camera and sweep it from one object to another (called a pan), that the result is a dizzying blur. Why doesn’t that happen when we sweep our eyes from one object to another? Try a little experiment. Stand in front of a mirror and look at your own eyes. Look first at one and then shift your gaze to the other. If you are like most people, you will not see your eyes move. What happens is that the little computer chip in the back of your eye momentarily suppresses vision. You only see when the eye stops.

It is a nice little design touch. We aren’t troubled with blurs as we move our gaze from one object to another. Try it. Scan the room where you are sitting. What seems like a camera pan is, to the eye, a series of steps, each accomplished neatly and without thought. Actually, it is more than a nice touch. It is an integrated part of a designed system.

Another surprise came when I learned that individual sensors do not always send a steady message to the brain. In fact, if the retina is steadily and evenly illuminated, there is very little going on in the optic nerve. Some of the sensors in the retina act like on switches, and others like off switches. The result is that the brain is not bombarded with unnecessary information. When light strikes a set of rods, a message tells the brain that the light is on. The rods don’t bother telling the brain anything until something changes. But the brain keeps telling you the light is on, even though nothing is coming up the optic nerve. This is how 150 million sensors can make do with 1 million wires to carry the message. They don’t use the wires all the time. Also, each rod and each cone has its own identity code, and ends up directed to its correct place in the vision center of the brain even if it is part of a mass of messages from many rods and cones.

While we rarely think about it, the eye is in constant movement. Some of that movement is so small it is hard to detect. But the eye must move to see. You may think you are staring fixedly at some object, but your eye is making tiny movements all the time. If you were able to fix your unmoving gaze on a black spot, it would disappear in a few seconds. The rods and cones adapt to the stimulus and switch it off. So it is necessary to move the eye enough to cause the image to fall on a new set of rods and cones every few seconds. And yet this must still keep the object in the center of your gaze without giving the impression of movement. All this is microscopic and computer controlled. You could not stop the movement if you tried.

Did you know you have a pulley in your eye? Of course you know that you have muscles that move your eyes. You are conscious of them when you move your eyes to extreme limits both vertically and horizontally. There are four of these on each eye, positioned above, below, and on each side of the eye. One would think that was enough, but there are two other muscles that run through pulleys and enable the eye to roll in the socket. If you tilt your head toward your shoulder, these muscles act to keep the eye vertical. One more nice little touch of design.

But the designer of the eye had other problems to solve. Of special importance is the fact that the amount of light striking a rod or cone is quite small, too small to provide the energy to create an electrical charge. How then, does the retina sense light? Through a simple chemical process. When exposed to light, the chemical substance of the retina breaks down into two other substances and generates the energy to turn the switch on. It takes about a half-hour in the dark for the chemicals to recombine—the period of dark adaptation.

We see through a complicated set of optics, a chemical reaction, computer enhancement, brain interpretation, and more. The eye turned out to be much more complicated than I had imagined. But the eye is useless alone. It is a part of system of vision.

Television is also a system for managing images. A video camera is useless by itself. It needs a system of cables, modulation, amplification, broadcast, reception, and display to be of any use at all. The same is true of the eye. The images that fall on the retina must be processed and transmitted to the vision center of the brain to mean anything.

In a video camera, an image is projected by a lens onto sensors in the back of the camera. This image is picked off in a series of sweeps by a beam of electrons and is coded and sent along a cable to a video screen. Here, a beam of electrons sweeps across a screen (400 to 600 lines per screen, depending on the system) and causes microscopic spots to glow in color. This produces an image on the television screen for us to “see.”

It is significant that the video system sees nothing. It simply transmits an image to be seen. The image is not real, it is just glowing dots on glass. Your dog does not see what you see when it sits in your lap and watches television with you. Animals sense movement and sound, but unlike you, they see no depth in the screen. In fact, you don’t either. But your system is designed and trained to interpret what you see on a flat screen in terms of depth and texture. The dog’s is not.

In the eye, an image is focused on the retina where it is sensed by 150 million rods and cones, computer enhanced and adjusted, sent to the brain and merged with the image from the other eye. But this combined image is not projected onto a screen to be seen. These images are processed by the brain and create in your mind, not a picture of the world around you, but the world itself. Look around. What you see is not a picture, it is real. You can move into it. It has texture, depth, color. Objects are related to one another in space. You can walk over to a table and touch it. It is precisely where you saw it to be. You will be able to predict how it will feel by the way it looks.

There are those who would tell you that all this evolved without conscious direction from a designer. They point to a wide variety of eyes, from the simple to the complex, and argue that development up the scale is possible. And yet, there is no evidence that such an evolutionary process ever took place nor any reason why it should have.

Furthermore, each of the eyes in nature is part of a system of vision. The eyes of birds, bats, fish, dogs and cats are all part of an intricate combination of complex subsystems. No part of these systems is of any value without the other parts. And no part of one system is of any value with another system. A bird would not profit from the eye of a fish. Having the eye of a man would not profit a dog. The hound would still lack the mental capacity to make use of what he could see. The human system of vision might actually make it hard for a wolf to survive. He needs his particular combination of senses to hunt, to eat, to live.

Phillip Johnson in his book, Darwin on Trial, summarizes nicely:

Some single celled animals have a light-sensitive spot with a little pigment screen behind it, and in some many-celled animals a similar arrangement is set in a cup, which gives improved direction-finding capability. The ancient nautilus has a pinhole eye with no lens, the squid’s eye adds the lens, and so on. None of these different types of eyes are thought to have evolved from any of the others, however, because they involve different types of structures rather than a series of similar structures growing in complexity.

Darwin on Trial (p. 35)

Evolutionists admit being baffled by the nautilus, which in its hundreds of millions of years of existence has never evolved a lens for its eye despite having a retina that is practically crying out for this particular simple change.

The eye did not evolve blindly. It was designed. It was designed by someone who himself could see, He that formed the eye, shall he not see? (Psalm 94:9)

When I took my encyclopedia back to the shelf, I placed it there with a sense of awe. Because that short article made it completely impossible for me to believe that such a system for seeing could evolve on its own. It was designed by an intelligence who knew that there was something to see. And he gave it to man, because he wanted man to see it.


Author
Ronald L. Dart

Ronald L. Dart

People around the world have come to appreciate Ron’s easy style, his non-combative approach to explaining the Bible, and the personal, almost one-on-one method of explaining what’s going on in the world in the light of the Bible. After retiring from teaching and church administration in 1995 he started Christian Educational Ministries and the Born to Win radio program.

Click here for more posts by Ronald L. Dart



Image Credits: Petr Novák