A test for deuteranomaly
Twice this past week I’ve been reminded of my deuteranomaly. I was diagnosed with it during my physical to enter college, and no, it isn’t contagious. I didn’t even know I had it for the first 17 years of my life. Deuteranomaly is “green-weak” color vision, the most common form of so-called colorblindness. It afflicts about 5% of the male population and is caused by a mutated form of the medium-wavelength “green” pigment in our retinal cones.
The one sure diagnostic I’ve found for my condition is the Ishihara 9. That’s the image on this post, part of the color test published in 1917 by Tokyo physician Shinobu Ishihara. If you have normal color vision, you should see the number 74 in it. I see the number 21 instead.
The irony is that in childhood I was often asked what my favorite color was, and I answered “green”. I can see the color green, but now I know that I don’t see it as vividly as others do. I have trouble discriminating small differences in hues in the red, orange, yellow, and green portion of the color spectrum, as they are shifted toward the red for me. So my favorite color was the one I could perceive less vividly than others did.
The most dramatic evidence of my condition came four years ago. I was attending a presentation on new textbooks and as part of it we looked at a text on a projected computer screen and the salesperson was pointing out how, with a click of the mouse, all of the verbs would change color to help poor readers identify them. She clicked to change her projected image of the text, and nothing happened. All of the words stayed their normal black – to me. I had to ask a colleague if there was a malfunction, and that brought a stare, first at the screen and then at me. We expect others to see what we see, but of course they really don’t, do they?
This past week I was surprised when a luncheon companion remarked about the green in my shirt – I only perceive it as gray and black, but she could see greenish hue hidden from my eyes. And today I’m recharging my Kindle 2 and am annoyed that I have a terrible time distinguishing when its LED light changes from the yellow “charging” status to the green “charged” color. Hardly much to trouble with, but it does point out the pitfalls of perception.
I am selfishly and naïvely convinced that I perceive the world accurately, but here is direct evidence that my senses are betraying me. Over time I’ve belatedly learned that a fellow teacher’s pickup truck and some of my hats, shirts, and socks were dark green, not black. My favorite Tilley hat is khaki, but where I see gray, perhaps others see green. When I take a picture of the greenery on a day hike, what do others see in it that I can only partially perceive?
And if my physical vision is biased, what about my other ‘vision’ – the philosophical one? In the certainty of my own rationalist viewpoint, firmly grounded in my senses, experiences, and flawed perception of the world, what am I missing that others may perceive? Is there something there, hidden from me by spiritual blindness? I don’t think there’s an Ishihara test for that.
MEADOR.ORG 
Twice this past week I’ve been reminded of my deuteranomaly. I was diagnosed with it during my physical to enter college, and no, it isn’t contagious. I didn’t even know I had it for the first 17 years of my life
One does not know what others experience, so what did you really discover in those tests.
The irony is that in childhood I was often asked what my favorite color was, and I answered “green”. I can see the color green, but now I know that I don’t see it as vividly as others do. I have trouble discriminating small differences in hues in the red, orange, yellow, and green portion of the color spectrum, as they are shifted toward the red for me. So my favorite color was the one I could perceive less vividly than others did.
Wouldn’t you have not known just how vividly others can see it? Do you like colours that look dull to you?
And today I’m recharging my Kindle 2 and am annoyed that I have a terrible time distinguishing when its LED light changes from the yellow “charging” status to the green “charged” color.
Have you came across bi-modal turn arrows found in some North American duristictions, such as Ontario?
My favorite Tilley hat is khaki…
Interesting one, I know there is something colour normal peolpe (including myself) have that you don’t, and I long suspected that there is you might have that colour normal peolpe don’t have, and I discovered this article. Does khaki look any more radient and mystical to you than colour normal people describe it?
Since I’ve never seen green quite the way most people do, I don’t know if that played any role or not in my early choice of a favorite color (which has since shifted to blue). I’m not familiar with the bi-modal turn arrows, and the article about those with the green pigment mutation seeing more shades of khaki is interesting. Khaki has always been a difficult shade for me, since it seems to vary greatly in how much green it shows – but then again, I’m green weak, so I’m always nervous about my color choices in clothing.
And also, I have been told that Deuteranomolous peolpe have more problems with colour on background combination than the colour itself. For example, if you were in the field and saw colour normal peolpe (with equal or greater visual acuity) looking for berries in the field, wloud you be able to make out what was going on?
I should add that many green LEDs on appliances like chargers often emit a yellowish tint, especially the older types. Yet green on LED traffic lights is normally much greener. Same with railway signals and navigation lights.
I am colorblind, but frankly, I don’t give a damn. There are perceptions that cannot be passed on to others. Colors are one of those perceptions. Matching some shade of yellow with wavelengths of light in the green and red zones of visible light, does not mean you are perceiving that yellow color the same way as the person who is testing your responses. Everyone perceives color in their own way even if they agree 100% on what that color’s name. It is like Plato said, we perceive the world like we are sitting in the back of a deep cave and all we see are shadows.
If you are having problems with your discrimination then you should do something about it. Choose a color to one you can perceive and matches its allotted task. Green for go, red for stop – that sort of thing. But if it is “Gee, don’t I look great in this purple suit with these yellow socks” sort of thing, well, there are more important things in life.
Do yau actually have blindness to any colour or just a weakness.
You have just shared everything I have ever experienced with my color blindness. When I was at work and my trainer was teaching me something about a program, he said that I would be able to see which boxes were required to be filled in. I had no idea what he meant until I had a brain blast and asked him what color all the boxes are. It turned out that they were all different colors (light colors such as green and yellow) and not all white like I thought they were. I also attended a review class with a powerpoint presentation and the lecturer said something about the “red box”, which confused me because everything was black. Lastly, I also had a shirt which people kept insisting was blue when I thought it was white.
My favorite color is also green. How ironic.