The Visible Spectrum… not exactly for everyone 

Juan E. Miranda Sanfeliz

In our Physics II course, we have studied many topics that go from electric current, magnetic fields, circuits, light, etc. Two topics that caught my attention were the visible light and the human eye. As to why I was attracted to them was, the beauty that is our eyes for the way they produce images for us, and the light for giving us those unique colors for each of those images.  In our course book, we can find information of two common defects of the human eye like myopia (nearsightedness) and hyperopia(farsightedness). Sure, these are very common amongst us and that’s why a lot people wear glasses of eye contacts, but the defect that I was curious is one not so common… colorblindness. 

For better understanding of this eye defect, is best if we remember how our eyes work. The human eye sees by light stimulating the retina. The retina is consists of a complex array of nerves and receptors that are called rods and cones. The rods give us our night vision, but can’t distinguish color. On the contrary, the cones perceive color during daylight conditions. These cones contain a light sensitive pigment sensible to wavelength that goes from 400nm to 750nm, also known as the visible spectrum.

Color deficiencies as many call it, can be associated with aging but nearly all color deficiency is hereditary. The most common form of color vision, the red-green deficiencies, has been proven to be due to sex linked X- chromosomes and simple recessive hereditary traits. What’s really interesting about this condition is that a color defective male always inherits his deficiency from his mother, even if she doesn’t have color blindness; she only is the carrier of the defect. The mother would receive the color deficiency gene from her father, only if he was colorblind, or from her mother that could be a carrier o colorblind, although that last one is very improbable.  

The rareness of this disease, if you call it that way, is the many types of colorblindness that they are. Many people think that if you’re colorblind you see everything around you black and white, like there was only one type of colorblindness. Fortunately for me, I knew to make this distinction because I had a History in middle school that was colorblind but his problem was with distinguishing between blue and yellow. One time, he was making a painting of a fairy with a blue dress for her niece and he ended up painting it green. Remembering that, I looked up different types of color blindness, or color vision deficiencies if you will. Base on clinical appearance, color blindness is described as total or partial.  Total color blindness is much less common that partial color blindness. Under the partial color blindness, there are those who have trouble distinguishing between and green and those who have trouble distinguishing between blue and yellow. The most common defects of the last ones mentioned are protanopia (absence of red retinal receptors), deuteranopia(absence of green retinal receptors, and tritanopia (absence of blue retinal receptors). An example of these deficiencies is given in the next picture: 

I know it may be sound a little awkward me seeing this, but I think is something really amazing. In our world, many things are distinguish by their color, like the grass, the clouds, the sky, to name a few, and to know that people out there haven’t seen difference. One time I was in the US for a vacation, and we stop at a red light. When I noticed, the red light had like a blinking white like in the form of a tube in front of the red bulb. I remember that I asked what was that and my cousin who lived there at the time told me that that was for the colorblind, especially the ones suffering from protanopia. After that I wondered if there was some kind of treatment for this so that people didn’t to depend on “the blinking light”. 

 

And so, like myopia and hyperopia, you can use lenses to adjust your color sensation because you can’t really improve color vision.  This concept of using lenses for correcting color vision deficiency dates back to the 1837 when a German scientist named Seeberg wrote about the possibility of correcting color vision deficiency using some sorts of lenses. But it wasn’t until the 20th century that different types of tinted lenses were developed to help colorblind improve their vision. As I mentioned before, these lenses can’t correct your color deficiency, just enhance your color perception. But like all things, it has its cons. Studies have found that color perception improves your problem area like red-green but at the expense of an increase in blue-green confusion, and that you might experience impaired judgment of distance and motion. Another con for these lenses is the cost, like $500 per lens, so not many people would be willing to pay such a high price for something that isn’t exactly a real solution for the problem, unlike a diverging lens that corrects myopia. 

Reading about all this, is obvious that I learned from this “rare disease” (around 5% to 8% of the world population is colorblind) like that it is a hereditary disease, that there isn’t a cure or remedy per se for it and why people with it choose just to go on with their lives like there’s nothing wrong, maybe just confusing one color with another.  But what I’m really interested is in meeting someone with total colorblindness and ask him questions like, “how your color vision deficiency has affected your performance at work?” and many others. If I had not read that part of the visible spectrum and of the human eye in our course book, I don’t think I would have read about this topic and want to look for my History teacher to maybe talk to him about something in his life other than his class.  And so, I think the Physics II course achieved its goal.  

References: 

• Giancoli, Douglas C. Physics for Scientists & Engineers with Modern Physics. 4th ed. Vol 1. Upper saddle River, N.J. Prentice Hall, 2009. Print.

• http://colorvisiontesting.com/color2.htm

• http://www.colblindor.com/2008/03/29/improving-color-vision-with-lenses-for-the-colorblind/

• http://www.colour-blindness.com/solutions/cure/