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Back to the Forum Archives In The Human Eye Part 1, I discussed the general structure of our eye. That is well and good, but let us get a bit more exact. Exactly how does the eye work to allow us to visually perceive the world around us? We can begin with rods and cones. Rods are important to us, but much less important than cones. The rod is a photoreceptive cell in the retina of the eye. These cells function as specialized neurons in the conversion of visual stimuli in the form of photons into electrical stimuli. For our purposes, a photon is just a specific quantity of light energy. A neuron is a nerve cell. The rods are sensitive to a wide range of light intensity. They are the cells responsible for perceiving size, shape, and brightness. However, rods do not distinguish color or fine detail. Hence they are most useful in night vision where color is usually absent. Our human eye will normally contain about 130 million of these tiny dells. Much less in number but much more important in our vision are the 7 million cones. A cone is a light-sensitive neuron with a conical projection in the retina of the eye. It is associated with color vision and perception of fine detail. Cones are less sensitive to low illumination levels and operate to allow bright light vision as opposed to night vision. They are concentrated at the central yellow body containing the fovea of the eye where we have no rods. At the outer edges of the retina there are very few cones. Chemical changes that occur when light strikes the cones are relayed as impulses to optic-nerves which lead to the occipital lobe of the brain. Occipital lobe simply means visual center. From our highschool science some of us may remember that color vision is the ability to distinguish between different wavelengths of light. Our visual apparatus works so that we perceive these different wavelengths as color hues. In fact, the human eye can discriminate very subtle differences in hue over the entire color spectrum from violet to red. How does this happen? It results from the fact that there are three different types of cones in our eye. Each of these types contains a distinctive type of pigment allowing it to absorb different colors of light. One cone absorbs red light, another green, and the third type blue-violet. A particular wavelength of light will stimulate all three types of receptors in different degree. Of course the pattern of these responses determines the color perceived. Considering these receptors we notice there are only three colors that can be detected. We call these the basic colors. The interesting thing about these three basic colors is they can be mixed in various combinations to produce all of the possible colors of our spectrum. Hence, three basic colors are sufficient. In our case the basic colors are red, green, blue (RGB) and we call this the RGB color model. There are other color models which are possible. For example, while our computer monitor uses the RGB model, our color printer will use the cyan, magenta, yellow, black (CMYK) model. This works equally well since the three basic colors (CMY) can be combined to produce all of the possible colors. Black of course is the complete lack of color and must be printed separately. The real difference between these two color models is the RGB model comes out of black and the CMYK model comes out of white. Black, as we noticed, is the complete lack of color. White, on the other hand is the combination of all possible colors. Notice, when it is not on, that our monitor is pretty close to black. In contrast our printer lays colors down on white paper to eliminate some of the inherent colors. One other color model is the red, blue, yellow (RBY) model that some of us learned in our studies of art. This model is equally valid for its area of application. If you had studied color televison, you would know this RGB color model is exactly what a color TV camera uses. Much like our eye, it has three different types of light sensitive receptors that respond to the three basic RGB colors. The light is converted into electrical impulses which are stored as an electronic image. This process is also the reverse of how the monitor you are looking at works. The monitor has elements at its visual surface which react to an electrical stimulation to produce a particular color of light. Then we see that light as a particular color. It's almost like magic. Now, in Macular Degeneration (AMD), as we said, all of this begins to go to pot. No one knows why although we sometimes call it age related macular degeneration. All that means is, old people are more likely to suffer from it. The other thing is, there is no way to tell how fast it will progress once it begins. On happy development is, people are working to understand this thing and some promising discoveries are beginning to surface. In one study, it was found that certain nutrients like zinc and certain antioxidants can act to slow the progress of the degeneration. It is not what I would call a big deal, but it is something and I am heeding the advice of the medical establishment on that. In fact, there is a pill form of supplement that provides all of the recommended minerals and vitamins. That is a beginning, but only a beginning. In another clinical trail, surgeons are implanting a miniature telescope in the human eye of some patients. This is a tiny device that magnifies images onto the retina and, in effect, reduces the size of the blind spot. As I said this is a trial procedure and it awaits long term valuation. For someone in my situation it would be foolhardy. If I could not see to write, I might consider it later. In another wild area of scientific progress we now have work being done in Artificial retinas. More and more research has been focused on developing artificial retinas or methods of stimulating the retina for those who have experienced permanent vision loss from retinal disease. As one example, one company is investigating an artificial retina type of microchip as a way of stimulating healthy retinal cells. For now that is another iffy but perhaps promising avenue to explore if and when my condition gets worse. It would have to be much worse for me to take that kind of risk. Invasive surgery is a last, not a first option. On another surgical front we have eye or retina transplant surgery. This is another case where we might easily do more harm than good. One problem with this procedure is inherent in the human eye. Once the person expires, the eye begins to degenerate immediately. It becomes completely useless in a matter of hours. When I think of that, I have a picture in my mind of surgeons lurking outside a dying patient's door like some latter day Frankenstein waiting for the last breath. Pardon me while I shudder. There is one other area that I mentioned briefly in the Forum
essay, To See or Not to See. This is about self healing and it
involves a new understanding of how our universe really works.
I have tried self healing before and I am convinced I made it
work. Since then, I have learned a great deal about recent scientific
developments. These tend to reenforce my ideas of life and energy.
I will get to these ideas in an essay I will call, Our Fluid
Universe.
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