The ability of the human mind to construct a 3D representation of your environment based on the information sent via the optic nerve from two eyes to the brain is truly remarkable.  Each part must function as designed in order for the system to work. 

I recently had the opportunity to ride in one of the newer Tesla electric cars.  The dashboard had a single touchscreen which displayed a perspective view of the vehicle itself – as if seen by a bird following the vehicle by 300 feet at about 100 feet in altitude.  The screen also displayed grayscale model representations of all surrounding vehicles, along with the markings on the road, the speed limit, nearby traffic lights, and other driving information.  In principle, you could drive the car without ever looking out the window by looking only at the screen.  Apparently, cameras surrounding the vehicle feed images into a computer which constructs a 3D virtual model of its environment, which is then displayed on the screen.  In other words, it does in a very limited way what your eyes and brain do with much higher fidelity every second of your conscious life.

The ability of the human mind to construct a 3D representation of your environment based on the information sent via the optic nerve from two eyes to the brain is truly remarkable.  Each part must function as designed in order for the system to work.  Human vision is therefore an irreducibly complex system and cannot have evolved in a neo-Darwinian fashion.  The eye was designed by God (Proverbs 20:12; Psalm 94:9).

Anatomy and Physiology

The human eye is a roughly spherical chamber filled with a transparent gel-like substance called vitreous humor.  A white outer layer called the sclera surrounds the eyeball except for a small region in the front of the eye, where the transparent cornea bulges out beyond the sphere.  Directly behind the cornea is the anterior chamber which is filled with a clear fluid called aqueous humor.  Behind the aqueous humor are the iris and lens.  The iris is the colored part of the eye which surrounds the dark pupil, and acts as an aperture adjustment which can rapidly change the size of the pupil.  The lens is gel-like and can change its shape so that light from external sources comes to focus on the retina – the light sensitive surface on the back interior of the eye.

An Overview of the Retina

The retina has two types of light-detecting cells called rods and cones.  These names are due to the shape of these cells.  Rods are relatively long and shaped like a cylinder.  Cones are shorter than rods and are indeed cone-shaped.

There are three different types of cones, each of which is sensitive to a particular range of light-frequencies.  One type of cones is maximally sensitive to blue light, another to green light, and the third to red light.  These three types of cones send electro-chemical signals to surrounding cells which combine the information into a signal sent to the brain which we perceive as color.  Cones are therefore necessary for our ability to see color.  They are primarily what we use when we read.  The human eye contains about six million cones.

Rods cannot detect color because they all are equally sensitive to the same color spectrum.  But they have other purposes.  Rods can detect shapes and (due to the way they are connected to other cells) motion.  Rods are distributed in the retina somewhat more evenly than cones, rather than being concentrated near the center of vision.  So, rods are very useful in our peripheral vision.  Rods also have a greater capacity to detect faint light than cones.  Therefore, rods are very useful at night or in other dark conditions.  The human eye contains about 120 million rods.

With a manmade camera, you generally need to choose whether you want to zoom-in on something in order to see it in great detail, or to zoom-out in order to capture a more panoramic view.  The human eye basically does both simultaneously.  But how can it do this without overwhelming the brain with information?  The answer has to do with the way rods and cones are distributed.

The cones in particular are highly concentrated near the center of our field of view.  In fact, the place on the retina that marks the center of our field of vision is packed with cones and has no rods at all.  This location is called the fovea.  When you look directly at something, its light falls directly on the fovea.  Since there are a great many cones in the fovea, we get a very detailed view of anything directly in the center of our field of view.  The ability to see small details is called visual acuity.

On the other hand, we have a lower density of light-sensing cells farther from the fovea.  This is why you cannot easily read text unless you are looking directly at it.  If you look away from this article, you will find that you can still see the article, but cannot read the words.  The visual acuity in our peripheral vision is much lower than near our center of vision.  This is how our brain avoids information overload, and yet we still have some visual knowledge of our surroundings.  It is an ingenious solution.

Muscles of the Eye

In order to see something in highest detail, we need to rotate both eyes so that its light falls on the fovea of each eye.  This is accomplished by six muscles attached to the external surface of the eye.  Four of these muscles you can control somewhat directly.  They allow you to look left, right, up, down, or any combination.  These four are each attached to the annulus of Zinn behind the eye on one end, and the other end is attached to the side of the eye upon which they pull.  So, to look left, the muscle on the left side of the eye flexes.

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