Sunday, July 03, 2011


The other day a few of us from the office went across to City Center Mall for lunch. The mall is gearing up to charge for parking, instituting barriers and operating a ticket system, but also put lights over each individual parking space. The light glows green if there is no car underneath it and red if there is a car parked there. It's a handy way to be able to see where the parking spots are, something that can be difficult to come by at the mall.

I was mentioning how much I thought it was a good idea and one of my Qatari friends said it wasn't that useful since there was little difference between the lights so it made it very difficult to tell. That made me pause for a second and I asked, "you don't see much of a difference between the red and green light?”. He said no, they looked similar. That's when it dawned on me.

I asked him, "Do you have red/green colorblindness?"

I'm sure most of you are aware that red/green colorblindness is pretty common in men, affecting anywhere from 1 in 10 to about 1 in 25 depending on ancestry. It's genetic, and is due to a defect on the X chromosome, which means a man inherits it from his mother. For a woman to suffer from colorblindness both parents would have to have the gene and pass it on so it is a lot rarer in women (because women are XX and the defect is recessive only if both X chromosomes have the defect will a woman get colorblindness, men are XY so only one copy of the defective X-chromosome is needed). I've known a few people who have had red/green colorblindness, which is why I think I spotted the issue right away with my friend.

He said he suspected he might be but had never been tested for it. So once we got back to the office I loaded up an Ishihara test from the internet (if you've never done one before I suggest you click on the link). The test shows you coloured circles and in the circles is a number, but if you have certain types of colorblindness you won't see the number and instead see a circle where everything is the same color. It's a pretty simple and ingenious way to test for colorblindness.

So my friend tried it and sure enough he couldn't see a number in most of the circles. He thought it was quite strange when I would tell him, “no, there is a number in it.” We called over some other friends and they took the test and all of them said the same thing. At this point my friend was a little bit shocked, not to find out he was color blind (he suspected that he was and one of his brothers would tell him that he was color blind as well), but that he couldn't see numbers in the circles whereas everyone else could. He told me it was like staring at a blank wall and then having everyone come along and tell you there was some number painted on it, yet no matter how hard you try you can't see anything. I could see how that would be disconcerting, we tend to believe in our vision more than any other sense ("seeing is believing”), which is why eyewitness testimony is considered so highly in court, so we may have a hard time believing that everyone else can see something that you can't (or even worse, you're quite sure you're seeing something but no one else is so they don't believe you). You’d be more inclined to believe it was a joke everyone was trying to pull on you.

So another Qatari told us that many men in his family are also colorblind (he wasn't) and that got me thinking if colorblindness was more prevalent in Qatar than in most other places in the world. The overall population of Gulf Arabs was never very large and they tend to be closely knit, usually marrying within their tribe, which would mean genetic conditions could be more common. Unfortunately a quick search of health websites had no mention of it, and government websites had nothing either. I would be curious though if anyone has any information on this please let me know.

My friend went home and had other members of his family took the Ishihara test. It turns out that one of his brothers is also colorblind, not too surprising since I think it's a 50-50 chance for any of his brothers.

To cheer him up a little I mentioned that there is at least one advantage to red/green colorblindness. A study indicated that certain types of camouflage were less effective against colorblind people since the camouflage was designed for fooling full-color vision. I've even heard that some militaries try to utilize this by having some colorblind individuals in units in the hopes that they might be able to see through any camouflage the enemy will be using. Couldn't find much about it on the Internet but the U.S. Army does accept colorblind individuals, though what jobs you can select are more limited. I don't think you can be a pilot though.



Anonymous said...

Could that explain why the authorities talk about the high incidence of running red lights? Colourblind individuals need to understand the position of the lights if they cannot clearly differentiate the red and the green.

Glen McKay said...

I think running red lights is because people want to. I've noticed where there are red light cameras nobody runs the light but if the intersection doesn't have a camera running the light is still common.