Tag Archives: cones

“What Color is This?”

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Throughout my life I have been corrected numerous times when stating the color of an object or material. Shades of purple and blue can get mixed up as well as shades of green and red. I am often corrected by my fiancé when picking out new clothing at a store, and there are even times when I have to ask her, “What color is this?” Although it can be frustrating at times admitting that I am wrong and my fiancé is right, this form of colorblindness has not affected me too much in my daily life. Maybe this colorblindness is a reason as to why I often chose neon colors as my favorite because they are the easiest for me to identify?

Unfortunately for my younger sister, this problem has become much more of an obstacle. During this class we have learned that red/green colorblindness can be hereditary and this has proved to be true for her as well. She is in her sophomore year at The United States Air Force Academy and recently found out she is red/green colorblind just like I am. However, she suffered immediate consequences regarding her future in the military. This colorblindness meant that she will never be allowed to pilot an airplane like she had once hoped. Many of the indicator lights in an airplane are small dots of red and green next to each other, so the slightest hesitation in determining them could prove deadly. Although I know this seemed like a huge setback for her at first, I believe she is handling it quite well. As a result of not being able to fly a plane, she has learned to fly her body, and has become an avid skydiver over the last year. She even is planning on helping me earn my skydiving license this summer.

This red/green colorblindness is a result of genetics. When light enters the eye is hits the rods and cones in the retina. The cones are responsible for color vision and contain photo pigments that respond to the amount of light that is hitting them. There are three types of cones in the eye that allow a person to see color when they send signals to the brain together. However, if any of the cones are deficient, then a person will not be able to see a full spectrum of color. My sister and I have most likely both inherited this from our parents due to a bad X chromosome. The difference is that I inherited this from only my mother because as a male I only have one X chromosome. My sister however, has received deficient X chromosomes from both my mother and father because she has two X chromosomes and still is red/green colorblind.

There are many tests to determine if a person is colorblind and the most popular is a dot test. These tests are often available for free online and can help a person gain some insight into their ability to see color. The following website has a free colorblind test for those readers who are interested.

http://enchroma.com/test/instructions/

Dark and Light Adaptation

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This spring break I travelled to Tucson, Arizona to visit some family. Tucson does not have very many clouds and most days have a clear sky and lots of sunshine. Since the sun is always shining your eyes get accustomed to the brightly lit environment for the length of the day. But while I was there we visited the nearby Kartchner Caverns. So when I went to the caverns and entered the dark, barely lit caves I couldn’t see a thing and my vision took a few minutes to adjust. After about three minutes my eyes were finally able to adjust and I could start to see some of the caves details. But it was a slow process and I felt impatient that I couldn’t adjust to the darker environment quickly. After touring the caves we exited back out into brightly lit desert and once again I was blinded in my new environment but this time my eyes were able to adjust and adapt much quicker than before. I was able to get a strong sense of my surroundings and was able to see clearly again within a minute.

The reason that our eyes adjust to light and dark at different rates is based on the properties of the rods and cones within our retina. Rods are very sensitive to light so when we are in dimly lit and dark areas we rely more on our rods to see, while cones on the other hand are less sensitive to light and are more dominant in well lit areas. Cones and rods also differ in their ability to regenerate, which comes into play in this scenario. Cones are able to adjust quickly as the pigment within them regenerates every six minutes, but rods are much slower. It takes their pigment about a half hour to regenerate. This difference in regeneration speed is crucial to difference between light and dark adaptation.  Since we use rods in dark places, it takes longer for our eyes to adjust to those places because the pigment takes so long to regenerate in our rods. But when going back out into a well-lit area, then our cones take over and we can adjust quickly to it’s the rapid regeneration of pigment that goes on within our cones.

So when I first entered the dark caverns from the bright desert environment my eyes had to adjust from light to dark which meant a transition from cones to rods. These rods took a while to adapt and adjust which is why I had difficulty seeing clearly for a few minutes. But once the rods within my retina were able to adjust then I had no problem seeing. And as I left the caverns and went back out into the sunlight my eyes had to once again adjust and switch back to the cones being dominant. Since the cones adjust much quicker I was able to see fine relatively quickly.