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Eyesight is one of the most complex actions of the human body. It is one of our most important surv

Out of Sight

by: Tyler Hass
Girevik Magazine (10/22/2002)

Eyesight is one of the most complex actions of the human body.  It is one of our most important survival characteristics and crucial for performance in any sport. While the eye is an incredible organ in its own right, the real act of seeing occurs in the brain. This is where visual data becomes the world that we know and interact with. The world's most powerful computers cannot do what our brains do instantaneosly, every moment of the day. The eye is merely the starting point for our amazing visual system.

In camera terms, the eye is really just two lenses, an aperture and film.  The two lenses are the cornea and thecrystalline lens.  The cornea is the larger and more powerful of the two, but it is fixed in place.  In order to focus on objects nearer or closer, we have the crystalline lens, which is pulled on by the ciliary muscles in order to change its shape.  Thus we have an adjustable lens system that sends a focused stream of light to the retina.  Before light goes through through the crystalline lens, it must first pass through the iris.  The iris regulates the amount of light that passes through, like an aperture.  It works by either constricting or dilating the pupil, which is a hole in the iris.  Light then travels through the pupil to the retina. The iris is also what gives our eyes color, depending on the genetically determined amount of pigment we have. 

This site provides a nice introduction to the anatomy and physiology of the eye. It provides nice descriptions of all the different parts of the eye and their functions.

Now that we have right amount of light and it is in focus, we now move onto the retina, which acts like the film.  The retina is the innermost layer of the eye and is composed of light-sensitive nerve fibers.  All of these nerve fibers send their collective data to the brain for processing via the optic nerve.  One interesting thing is that after passing through the lens, the image comes in upside down.  The brain corrects for this optical effect. Also, data from the right half of your field of vision is processed in the left hemisphere of the brain and vice-versa.  The key idea here is that the eye itself is just an instrument for collecting data, like a camera, but the brain creates the final image.
For functional purposes, the retina is divided into three critical zones: the fovea, the macula and the periphery.  If you stretch your arms out in front of you and place your fists next to one another, you can approximate the size of the visual field occupied by the macula.  The macula is responsible for seeing sharp details that require focused attention and colors.  At the center of the macula is thefovea, an extremely dense array of nerve fibers.  This area is about the size of the head of a pin, but there are 160,000 nerve fibers per square millimeter in this area.  If you focus on a line of text, notice that you cannot see its neighboring lines as clearly.  This demonstrates how small an area that is covered by foveal vision.  Combined, the macula and fovea comprise our area of central vision, or conscious attention.  In the periphery, concentration of nerve fibers declines as you extend out to the edges of our field of vision.  The density is not sufficient for reading or even recognizing most objects.  What peripheral vision does is let us know when something is happening outside of our area of central vision, so that we can then focus in on that area with our sharper central vision.  This is called the Visual Grasp Reflex and explains why we always have to look when a pretty girl walks by (we can’t be blamed for looking at other women, it’s hard-wired into our brains!).  Our central and peripheral vision are processed separately by the brain. Essentially, we have two distinctly different vision systems that perform different functions, yet we end up with only one final image. It is still unknown where these two images actually become one, because the data sent to the brain is processed in many different regions of the brain.  

Here you can see a simulation of what our daytime vision looks like. Most color and detail is concentrated in the central region. In the periphery there is very little color perception and less acuity.

At night, the Fovea does not receive enough light to provide any visual information. However, because the periphery is composed of rods, it works quite well in the dark. Vision in the macula becomes black and white only, because the cones do not function well in low light.

 Humans also have two types of photosensitive nerve cells, rods and cones. Rods are used for sensing the intensity of light and cones are used to detect colors.Additionally, we have three different types of cones: red, green and blue.  These cones can be very densely packed for seeing fine details, but they require a lot of light in order to function.  It is believed that rods are the more primitive of the two, along evolutionary lines.  Scientists believe that rods evolved first, so that creatures could hunt at night.  Most animals tend to have large amounts of rods and very few cones, if any.  For this reason, scientists know that some animals are essentially colorblind.  Some animals can see colors, but only within a certain spectrum because they only have two colors of cones.  Few animals have three cones and even fewer have more than three cones, but the ones that do can see a larger percentage of the light spectrum, including infrared light and/or ultraviolet.  The problem with cones is that they only work in a well lit environment, such as daylight.  Rods on the other hand function well even at night, because for each nerve cell, there can be many rods connecting into it. Each cone connects into one nerve cell, creating a 1:1 ratio that makes cones favorable in perceiving fine details, but only in a bright environment. Central vision is comprised of densely packed cones and a relatively small number of rods.  In fact, there are no rods at all in the fovea.  Peripheral vision is comprised of mostly rods, with the concentration of cones being almost zero in the outermost portion of our field of vision. 

The human eye can detect 20 different hues, 200 levels of saturation and 500 differerent brightness levels. However, our ability to differentiate colors declines in extremely bright or dark conditions, so the circles become more narrow.

For more information on visual perception, check out this site: The Physiology of the Senses:
Transformations for Perception and Action
. It is interactive and very informative. By far one of the most interesting websites I have ever seen.

As a result, our peripheral vision works extremely well in low light, but it has poor acuity and is colorblind. As a result, our peripheral vision is used mainly in the dark and for detecting motion.  Rods are so sensitive that they can detect a single photon and see the light of a candle from ten miles away.  This explains why you often see things moving out of the corner of your eye at night, but then they disappear as soon as you turn to look at them.  You central vision, with its cones, simply cannot pick things up in the dark.  Thus, you can see the importance of having two vision systems.  Another interesting thing about our two vision systems is how they are processed.  If you divide our brain into the conscious and subconscious, you could say that cone (central) vision is processed consciously, whereas rod (peripheral) vision is processed subconsciously.  At most times, your subconscious mind functions in the background, sifting through huge streams of information for your conscious mind to consider.
  It is believed that the subconscious mind can process thousands of times more information than the conscious mind, which can typically focus on 7 things at once, sometimes more or less.  The subconscious mind is extremely powerful and fast, but it is almost ignored in our society.  Our educational system is focused on cultivating rational thinking and conscious living.  Very little attention is given to the more primitive subconscious, but it was not always that way.  If you have ever seen an old Japanese painting of a Samurai warrior, you will notice that they are usually fighting cross-eyed.  This is not merely a stylistic interpretation.  Musashi, author of the “Book of Five Rings”, was a famous warrior and won over 100 duels. He noted that he fought his best when in this state.  The reason behind it is that rod vision is extremely good at picking up motion.  Some people call this preconscious processing. When looking at things peripherally, you tend to respond to more subtle cues, such as an opponent shifting his weight, holding his breath or tensing a muscle.  Even before he starts moving, the subconscious mind has picked up on the chain of events before it has even occurred.  Thus, many warriors believe in the power of preconscious processing.

This image appears to be a random pattern, but it actually becomes a 3-dimensional image when you look at it with diverged eyes. For more stereograms, check out Eye Tricks.
Also take a look at Scott Sonnon's Flow State Performance tapes from the Fisticuffs package. He uses cutting-edge perception training for enhanced combat performance. Available from RMAX Productions.


Vision Training Methods

There are many types of eyesight training programs on the market today, some for correcting vision problems, others for improving sports performance and even some for learning.  The most common one is the Bates Method.  Most training programs that advertise on TV and tell you that their exercises will allow you to throw away your glasses are based on this method.  It has been around for a long time and has had many incarnations, but there has never been any research to support its efficacy.  Most ophthalmologists believe that this method simply does not work.  They do not think it is possible to train the muscles of the eye to alter the shape of the cornea.  The best therapy currently available is Lasik, which uses a laser to correct the shape of the cornea. Lasik has been used successfully by major league baseball players, extending the careers of players like Wade Boggs.  They report crisper vision and enjoy not having to worry about contacts.

There is a new training program available called Vizual Edge that trains your eyes not for better vision, but for better seeing abilities such as tracking, diverging, converging, depth perception, alignment and recognition.  It was invented by ophthalmologist Dr. Barry Seiller, who has also performed over 3000 Lasik surgeries.  He has worked on performance vision training with a variety of Olympic, professional and collegiate athletes.  In one experiment, he tested a high school baseball

For more information on the Vizual Edge Perfromance Trainer, visit theVizual Edge website.


team using his vision skill assessment program.  Based on the scores, he was able to pick out all of the top hitters on the team.  Dr. Seiller calls his Vizual Edge program “weight training for the eyes”, because you develop strength, flexibility and coordination in the ocular muscles.  The Vizual Edge program uses a few different computer “games” and a simple string device for training your visual skills.  I tried the program for 15 days, but it was too short to experience any conclusive results.  I thought the program was well designed and it comes with nice 3d glasses.  My only complaints about the program are that you cannot track your progress over a long time period and I did not see any differences between the programs for different sports.  This field is still in its infancy, but hopefully it will grow, because it holds great promise.

Hawkeen training is a method of learning to use your peripheral vision.  What they do is place a bead on the end of a stick so that the bead hangs 12 inches from your eyes directly in the center of your field of vision.  You then fix your gaze upon this bead and start to walk around, guided only by your peripheral vision.  It feels strange at first because you see a double image, but your brain knows what to do and your feet always land in the right places.  Eventually they they do this exercise at night, using a glowing bead.  Nightwalking is reported to be quite incredible.  Because you are so tuned into your peripheral vision, you will see things you have never seen before.  People report seeing owls fly over head and various other creatures of the night. They also report incredible feelings of calmness and euphoria when doing this training.  While this might seem incredibly strange to us, it might not seem so foreign to our ancestors who hunted at night.

Lastly, peripheral vision has also been used for reading at incredibly high speeds.  Some experts have been able to read faster than a page a second with 70% comprehension. Photoreading is a technique where you diverge your eyes while reading a book.  By looking through the book, it will appear out of focus, but this is because your rod vision has taken over.  The theory is that instead of using your limited conscious focus to read, you tap into the vast power of your subconscious.  The program also includes a variety of different methods for using your conscious mind to access the information that has been processed subconsciously.  Thus, the system emphasizes using the whole mind, as opposed to just using the conscious mind.  In my own experience, the technique can work, but it requires a lot of practice to get it down.


Check out Tyler Hass article on vision training

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