Color Vision
Roses are red, violets are blue. But why? What makes the eye see the colors it does and how? First we must understand the basic structure of the human eye.
The cornea is the outside membrane of the eye covering the iris and the pupil. The iris is the colored part of the eye and the pupil is where light enters the eye and enables us to see. Just behind the pupil is what is known as the lens, this corrects what we perceive through the eye and refracts the light we see into the retina covering the back of the eye. In the back of the eye is the optic nerve which directs the signals of what we are seeing to the brain to finish being interpreted and allows us to see everything around us.
Now, the retina is covered with tiny cells called cones and rods. Right now, we’ll only be discussing the cones, which are what give us the color vision. Humans have three types of cones that allow us to perceive colors; those cones are the yellow (or red) cones, violet (or blue) cones and green cones.
When light hits our eyes, it refracts through the lens in the eye to the retina on the cones. The various colors come from what is called the visible spectrum, which is a smaller part of an entire standard of wavelengths of different sorts, but that’s a different discussion. The visible spectrum consists of every color able to be perceived by a human being.
How does that work, one might ask? As mentioned before light passes through the cornea and the lens focuses the light onto the back of our eye. When the light hits the back of our eye the retina, covered in rods and cones, converts the “light into corresponding electrical signals” (“Light and the,”) which goes to our brain for further interpretation of the signals.
Now rods are what allow us to see detail in everything we see throughout the day. “They are responsible for our dark-adapted vision” (Nave). What this means is that at night and in dimmer lighting, we don’t see as much color vision as we do shadows and detail. Color vision requires bright light while detail and shadow vision does not need as much light. To be able to see considerable well in darkness, it rakes about “30 minutes or longer, because the rod adaptation process is much slower than that of the cones” (Nave). Also, there are many more cones than rods right around the optic nerve. However, there are no rods and cones over the optic nerve, which give every eye a blind spot.
This blind spot is where you cannot see anything, for obvious reasons considering there are no rods or cones there. The blind spot is mainly in the peripheral vision, which surprisingly enough doesn’t have color vision. The reason being is because in our peripheral vision there are far more rods than cones.
Colorblindness
Now there can be problems with color for some people, including myself. Some people lack certain cones in their eyes or lack the use of those cones making them see colors very differently than the rest of the world. Another term for colorblindness is “Dyschromatopsia” (“Color vision: one,”). John Dalton, an English meteorologist and chemist actually had colorblindness and could only see the color yellow (“Color vision: one,”).
There are many types of colorblindness. Regular vision is trichromatic with three colors, whereas colorblindness can be dichromatic or monochromatic, with either two or one color. There are three types of dichromatic vision: deuteranopia with no green cones, protanopia with no red cones, or tritanopia with no blue cones (Lambert). People with monochromatic vision truly do see the world in black, white and grey like you would think when hearing colorblind. There are two types of this vision as well: achromatopsia, which is poor vision, and nystagmus, which gives you literal googly eyes (Lambert).
Think you’re colorblind? Take the test! See what you can see in the picture below.
Works Cited
Color vision: one of nature’s wonders. (n.d.). Retrieved from http://www.diycalculator.com/sp-cvision.shtml
Gouras, P. (2009). Color vision. Webvision: the organization of the retina and visual system, Retrieved from http://webvision.med.utah.edu/book/part-vii-color-vision/color-vision/
Lambert, K. (n.d.). How colorblindness works. Retrieved from http://science.howstuffworks.com/life/human-biology/colorblindness1.htm
Light and the eye. (n.d.). Retrieved from http://www.handprint.com/HP/WCL/color1.html
Nave, R. (n.d.). The rods and cones of the eye. Retrieved from http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html
The Things Seen, Heard, and Felt 
This is like a review from yesterday’s class! Awesome! Like I said before in class, I know all too well about this color blindness from my father. When he was younger he used to tell me that he saw red as black but he says that now he sees it has normal. Don’t ask me how! But the colors he has the worst time with are Green which he sees as a grayish pink and light blue he sees as a pink. I guess that explains why he hates pink so much! I guess according to your blog he has a form of dichromatic vision which is deuteranopia with no green cones, since all green colors he sees as different. Thanks for sharing!
This topic reminds me of freshman year in high school and my biology class and I remember doing a lab on colorblindness and trying to figure out whether any of us were colorblind. It turned out some people can be partially coolorblind much like Fracheska’s dad I guess where the colorblindness differs from a specific red-green or yellow-blue colorblindness and only applies to some colors. One bit of information that i found surfing the web has to do with yellow-blue deficiency and the ways that people with this color-blindness much like yourself see the world.
Thanks for posting this blog and sharing your own personal story it super interesting!
This is what we just learned in class! It is very interesting, well at least I think so. I am tested for colorblindness every year when I visit my eye doctor. But I have always wondered how people first discover that they cannot see all colors, or do not have three cones in order to see all colors. I did not see an eye doctor regularly until I was 16, when I started having vision problems, so how would one discover that they are having these issues if they did not. I think it’s great that people can adapt to the way they see things even if it is not how others see things. Although I often wonder if anything I see is like what anyone else sees, since there is no real way to test how others are seeing things. Thanks for sharing your story, great blog!
It seems that there are individual ranges for our particular cones over which we each see colors. Even those who have a 4th cone might only see slightly more colors if that particular cone overlaps the range of one of the others.
John Dalton actually did a lot of preliminary work on colorblindness after he realized that he did not see colors as others did – I wonder how he realized this difference? He became so associated with this that for quite a while, colorblindness was called “daltonism”.
There are few who are truly colorblind and who only see the world in gray-scale, like pre-1960’s TV. Since our man-made world is actually dependent upon color coding to quickly access information and to sort it into categories, one could be at quite a disadvantage.
Neil Harbisson, an artist, is truly colorblind. Until he went to college and met cyberneticist Adam Montandon. Together, they worked on a device that would enable Neil to “see” color through tones. His device’s range even includes waves outside our normal color range.
(http://www.ted.com/speakers/neil_harbisson.html)
Here is a TED Talk by Harbisson. I found it especially fascinating that he is so attuned to his device that he even dreams in tonal color now.
“I Listen to Color”
Well…THAT didn’t work — here’s another try at getting the link for “I Listen to Color”:
Last try – here’s the regular link:
Good to see that topics at the blogs complement each that complement our blogs, another somehow. This issue of the conditions of vision caused by the absence of any quantity of cones at the retina, although it seems unusual for many, for sufferers is a source of restlessness and in many cases suffering. I met a colleague at work who suffered a disorder of colorblind type in his vision and saw the blue as green and red as blue, and having to prepare Ethernet wires (which follow a strict code of colors) he always needed someone to lean on to validate what he saw.
That’s good to remember that even though people have not chosen the condition in which they live, we can give a helping hand in any case. Thank you!