My own research into many sites, information is pieced together

Colorblindness is defined as the inability to perceive colors in a normal fashion. Colorblindness is an inherited condition that is sex linked recessive. As a result, very few women are colorblind but approximately 1 in 10 men has some degree of colorblindness.

The most common form of colorblindness is red-green and has a wide range of variability within this group from very mild to extreme. The second most common form is blue-yellow, and a red-green deficit is almost always associated with this form. The most severe form of colorblindness is achromatopsia, the inability to see any color, and is often associated with other problems such as amblyopia (lazy eye), nystagmus, photosensitivity, and extremely poor vision.

Symptoms

  • The inability to see colors with the same intensity as normal individuals

    There is no known treatment for colorblindness. People with this condition need to learn to cope. Colorblindness is a life-long condition.

  • The term has also become an overused-to-the-point-of-cheesiness analogy for loving people regardless of race/skin color.

    Color blindness occurs when certain color-sensing cones in the retina fail. The retina in the human eye is covered, with varying densities, with light sensors called rods and cones; rods detect the level of brightness in the light striking them, while cones detect color. Certain cones detect red light, others blue, and others green. If one set of these cones fails to detect light properly, however -- say the red cones fail, so that purple and blue colors are indistinguishable -- then color blindness occurs.

    Under normal conditions, most people can match any color in a test stimulus by adjusting the intensity of three superimposed colored light sources (blue, green, and red). The fact that only three colors are necesary to match all the colors perceived is a reflection of the fact that our sense of color is based on the relative levels of activity in three sets of cones with different absorption spectra. For about 2% of the male population and 0.03% of the female population, color vision is more limited. Only two colors of light are needed to match all the colors that these individuals can perceive; the third color is not seen. Sich dichromacy, or color blindness, is inherited as a recessive, sex-linked characteristic and exists in two forms: protanopia, in which all color matches can be achieved by using only green and blue light, and deuteranopia, using only blue and red. In another major class of color deficiencies all three wavelengths are needed, but the matches are made using values that are significantly different from those used by most people. Some of these anomalous trichromats require more red than normal to match other colors; others require more green than normal.

    The genes that encode the red and green pigments in the cones of the retina lie adjacent to each other on the X chromosome and show a high degree of sequence homology. In contrast, the blue-sensitive pigment gene is found on chromosome 7 and is considerably different in its amino acid sequence. This suggests that the red and green pigment genes have evolved relatively recently. This genetic knowledge also explains why most color vision abnormalities involve the reg and green cone pigments, while the blue cone pigment remains relatively stable. Because they are located adjacent to each other on the X chromosome, crossing over during meiosis can result in an unequal distribution of the genes such that one chromosome contains multiple copies, while the other contains none. Crossing over can also result in hybrid genes that code for pigments with different absorption spectra.

    Human dichromats lack one of the three cone pigments, either because the corresponding gene is missing or because it exists as a hybrid of the red and green pigment genes. For example, some deuteronopes lack the green pigment gene altogether; others have a hybrid gene that is thought to produce a redlike pigment in the "green" cones. Anomalous trichromats also possess hybrid genes, but these are thought to elaborate pigments whose spectral properties lie between those of the normal red and green pigments. Thus, although most anomalous trichromats have two distinct sets of long-wavelength cones (one normal, one hybrid), there is more overlap in their absorption spectra than in normal trichromats, and less of a difference in how the two sets of cones respond to a given wavelength.

    These are my lecture notes. Please feel free to use them elsewhere with attribution.

    I've been wondering about something like this for a long time, and I have a theory.

    If a person perceives colors differently from the rest of the world, they'd never know it. I mean, that's how colors have appeared to them their whole life. If they see a color that they know to be red, and someone else looks at the same red and sees something different, neither person would be aware they're seeing anything different than the other person. Each would assume the other sees the same thing.

    What I'm saying is, both people can look at something and each person sees a totally different color than the other. One person says "That's red." The other person says "I know."

    Therefore, it's possible that your perception of the color red is totally different than another person's perception. However, it's universally agreed to be red, because that is the association you have made with that color for your entire life. Back in your early years, someone pointed to that color and said "Red", and you made the association.

    This means that it's possible that everyone sees colors differently. What looks red to you might look green to someone else, and you both would never know it.


    Noder's Note: I'm not saying this is the way it is. It's merely a possibility.

    As someone who's been tested at 70% red/green colorblind, I have often tried to explain to people with normal color vision what it's like to be colorblind. The best explanation I have come up with:

    1. If you give me a box of 8 unlabeled crayons, I can sort them.
    2. If you give me a box of 16 unlabeled crayons, I can sort them.
    3. If you give me a box of 32 unlabeled crayons and good light, I can sort them.
    4. If you give me a box of 64 unlabeled crayons, I'll give you back about 50 piles.

    There are some odd effects, like not being able to distinguish some shades of purple from blue due to just not seeing the red component.

    Color blindness is most often the inability to distinguish between red and green. Less often a person will have problems with blue. A common misconception is that color blindness is the complete inability to see any color and that the person in question can only see white, black and shades of grey. This is simply untrue. Many color blind people can see the specific color, they just have a hard time distinguishing it from other colors. Only one in one thousand cases of color blindness are people who truly see in monochrome.

    The cause for color blindness is genetic, and it has to do with the rod and cone light receptors in your eye, most people have 74% red cones, 16% green, and 10% blue. People with color blindness may have a reduced amount of receptors or in come rare cases no receptors in the specific color at all.

    Basically to learn more (http://www.toledo-bend.com/colorblind/index.html), and to take a color blind test (http://www.toledo-bend.com/colorblind/Ishihara.html). They also have color swatches of commonly accepted colors and their names. Enjoy.



    Info from (http://channels.netscape.com/ns/atplay/colorblind.jsp)

    As well as a physiological handicap, "colour-blindness" is also the name of an often-proposed "solution" to racial discrimination in contemporary America.

    It is understandable to assume that eliminating the ability to socially differentiate between races would end racial prejudice. However, one must realise that attaining equality among races cannot be solved so easily. Racial discrimination has firm roots in history, modern economics, and many different American subcultures. None of these could be realistically eliminated by colorblindness.

    During the colonisation of Africa, there existed a strong sense among Europeans of what English poet Rudyard Kipling called the "white man's burden". This phenomenon was the idea that Europeans had a divine right to reconstruct African culture based on Christian aristocracy and/or European social standards. The European colonisation of Africa inevitably ended with the destruction of myriad elements of indigenous African culture. This grand anthropological casualty stemmed from the original belief that the lifestyle of European aristocracy was in some way superior to that of many different African peoples.

    The similarities between the motivations and justification for colour-blindness are remarkably similar to those of the "white man's burden": they were both blinded to cultural and ethnic differences; and attempted to mend this gap of understanding by ignoring others' individuality. Because individuality is a bad thing, right? So let's not acknowledge it.


    shaogo has pointed out my mistake of misinterpreting "a person's color as being part of their individuality." On a personal level, someone's ability to evaluate another's persona should have nothing to do with the colour of their skin. On a more political and economic level, however, I believe that color blindness may or may not be as effective, depending on the situation at hand. Kudos to shaogo for taking the time to correct me :)

    Color blindness and the Ishihara test (thing)

    Some people have impaired color perception, called color-blindness. Studies show women are rarely affected, and around 15% of men have some color-blindness. That difference is related to the X chromosome. Women have two X's, men have one. If a man's one (recessive) X chromosome is a little different, vision can be a different picture.

    A few cases of color blindness are related to medical conditions, but the common cause is genetic. The result can be various types of color blindness. Red/green color blindness is most common.

    I think the term "color blind" is a misnomer, because most color blind people do see various colors, but their total color perception is different. It's extremely unusual for sighted people to see no colors at all, although there are very rare reports of people who can see, but see little or no color. I think that is total color blindness.

    So, what's going on here?

    The non-color light sensors in the eye are called rods. The rods detect shades of gray, and are more important for night vision.

    Color is seen by parts of the eye, called cones, detecting different frequencies of light. Studies confirm that different cones have peak light detection at 3 different wavelengths. A blend of signals from the cones, detecting different frequencies and intensities of light, produces color vision.

    I know my color perception is decidedly not normal. I can describe what's it like for me.

    Good news, I think someone can be "color-blind" and rarely notice it!

    Really, it only seems to bother other people when they notice I don't see things quite the same way. Well, it's better than being totally blind (unless you're Stevie Wonder, maybe?). I guess most people don't need to worry much about it, if it's not a bother to them or other people.

    There are some web sites that have the Ishihara test plates.

    So, see for yourself. (Don't worry about the French, scroll to the bottom, it's all numbers.)

    There are many other websites that have color tests, it's not hard to find the Ishihara test.

    If you see numbers in all those dots, which is likely, then good for you, because to me almost all of them are just a bunch of dots. What one person sees is not always the same as what others see, and some cannot see that-- What can't be seen, well, you can't see it!

    I have difficulty differentiating reds and greens. This does not mean I can't see reds and greens. Put me in front of a red brick wall, or a green field. I think I see red and green. They definitely look different to me, when I can see them! Sometimes I need a broader expanse of color or else I may not see it. In order to see little red berries on a big green holly bush, I may need to get closer. That must be because I have a different distribution of those cones, compared to most people.

    I discovered my color blindness when I was six. My grandfather brought home a book with the Ishihara color plates and showed them to me.

    I never thought much more about it until a couple years ago, when I found some Ishihara color test plates on a website and reviewed them. Again, confirmation I do not see colors the way most people see them. I printed some of those on glossy photo paper, and showed them to about twenty friends, a mix of men and women. None of my friends had as many problems as I did seeing things "normally", although a few of the men noticed they didn't see some things.

    For me, the most interesting Ishihara plates are the ones that have two different numbers represented in the colored dots. You might see either 29 or 70, or maybe you don't see any numbers at all!

    I'm OK with that, a bunch of dots where different people say they see different numbers, and I don't see any numbers. Where's the problem? Heh.

    It's nice when people notice I am color coordinated when it comes to dress, fashion and design. Maybe that is compensation. I try harder, I have to think about color. You will never catch me wearing a white T-shirt! I guess there is a point there, color blindness has never really bothered me, and that's what I hear from others who have it.

    I am used to not always seeing some of the things that other people see, tulips out in a field, raspberries on bushes, or berries on holly. They might mention them, and I squint a little and say "They are pretty for you to mention them", or I might have said, "I can't see that", but I've learned not to do that, it sometimes makes others uncomfortable.

    When I showed the Ishihara color plates to my friends a couple years ago, and told them that I did not see the numbers in them, some of them said they felt sorry for me, and I was quite surprised. It was touching. I told them not to worry, it's never bothered me.

    Update:
    Regarding the genetics, there are a couple other ideas that seem to make sense. Women are less affected, so think about a hunter-gatherer society and imagine who's doing what: women gather fruits, berries and, nuts, while the men chase down the game? There are also references somewhere about modern military research indicating color-blind men are better at distinguishing camouflaged targets.

    Update:
    Color perception is unique to every individual, because every eye has a different mixture and distribution of varying cones and rods.

    Update:
    It finally dawned on me computer users with color blindness can tweak RGB in the display monitor screen, to see "more normal" images. So, I bumped up the red a good bit, lowered the blue a bit, and see more on the screen. I will continue to tweak this. Perhaps one day I will be able to see all the Ishihara numbers, on my computer screen.

    Col"or-blind (?), a.

    Affected with color blindness. See Color blindness, under Color, n.

     

    © Webster 1913.

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