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" (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.
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