Unreliable Secondary Color Vision Tests for Pilot Candidates

If you want to acquire a pilots license, you need to pass medical checkup including a color vision test. If you fail the color blindness test you will get a second chance with a different color vision deficiency check. Unfortunately some researches from the United Kingdom could show, that those secondary color blindness tests are not reliable enough.

Joint Aviation Authorities
Joint Aviation Authorities

The Joint Aviation Authority (JAA) in Europe is the counterpart to the Federal Aviation Administration (FAA) of the United States. The JAA provides the standards of safety in aviation, including the rules on color vision tests for pilot candidates.

For the first color vision screening a set of 24 Ishihara plates are used. If you can identify the first 15 plates correctly without any hesitation you will pass the test. If not, you will get a second chance to find out if your color vision abilities are good enough.

The second test differs between countries. There are four different secondary color blindness tests approved by the JAA and in use:

  1. Nagel Anomaloscope
  2. Holmes-Wright Type A lantern
  3. Spectrolux lantern
  4. Beyne lantern

The anomaloscope is based on matching yellow to a mixture of red and green whereas you can adjust the brightness of yellow and the red-green mixture. The lanterns on the other side consist of several colored lights which have to be identified correctly. They are simulating signal lights used in aviation.

If you pass the second color blindness test you fulfill the color vision requirements for pilot candidates. Therefore one should think that those four tests are leading to the same result. But they are not.

A team around Prof. J. L. Barbur of the Applied Vision Research Center, City University, London, researched those different color vision deficiency tests (Color Vision Tests for Aviation: Comparison of the Anomaloscope and Three Lantern Types).

Secondary Color Blindness Test Results for Deuteranomalous Trichromats
Secondary Color Blindness Test Results
for Deuteranomalous Trichromats

As the results on the right hand side show, it depends on the color blindness test used in your country if you will pass or fail the test. The table shows pass/fail rates on all four secondary color vision tests for people suffering from the most common type of color blindness—deuteranomaly.

The researchers could also show, that all participants with a severe color vision deficiency will fail the tests. So the problem resides only for people with some mild form of color blindness.

Consistency is lacking in color vision testing and an aspiring professional pilot may be accepted without limitation in one country, and rejected outright in another. The different tests also reveal different aspects of color deficiency and the severity of outcome may or may not relate directly to the subject’s ability to discriminate colors.

As a conclusion it can be said that a more reliable and less variable internationally accepted color blindness test has to be found.

Do Colorblind Women Have Colorblind Children?

Sometimes a woman finds out about her color blindness and in this case, she is often worried about what will happen to her children.

What is the chance for them to inherit her color vision deficiency? Or is there any possibility at all that they will not be colorblind?

When I had found out that I was colorblind some questions grew to my concern. Apparently I’m red-green colorblind but I honestly don’t see it as a disadvantage on my part. I feel like I see those colors just fine. However when it comes to taking those Ishihara tests I feel almost handicapped for not being able to see them.

Anyways my question was, should I be worried about having colorblind children in the future? I haven’t read much about color blindness and genes but since I am colorblind, then I carry this abnormal gene, right? So if I were to have children with a colorblind male wouldn’t our children be, in fact, colorblind?

Before I answer your questions about the color vision of your children I would like to say a few words about the statements above. If you don’t feel handicapped in everyday life and if you feel like seeing colors just fine, the same will be true for everybody else inheriting color blindness from you.

The above explanations sound like a slight form of color blindness. There is a huge range starting from very slight color vision deficiency up to complete color blindness. The most important about this is that your children will inherit exactly the same type and severity of color blindness as you are suffering from.

Now let us have a closer look at the above questions about inheriting color blindness from a mother to her children:

Do I carry this abnormal gene encoding red-green color blindness? Yes—and that’s not all. You have not only one but two chromosomes which carry the information. Women have two X chromosomes also called sex-chromosomes which encode red-green color blindenss. If only one of them would carry it, you wouldn’t be colorblind.

Should I be worried about having colorblind children in the future? Firstly you don’t have to be worried at all. As I wrote above your color blindness is not very severe so your children will carry the same form of it. So there is nothing to worry about. But you are also right that there is a chance of having colorblind children.

If I were to have children with a colorblind male wouldn’t our children be, in fact, colorblind? Yes. In this case all of your children would be colorblind—if your partner is also red-green colorblind, which is by far the most common type. And in the case that he isn’t colorblind all of your boys would inherit the color blindness from you and would also be colorblind but all your girls wouldn’t be colorblind, because they inherit a normal gene from their father which overrides the abnormal one inherited from you.

To conclude, if you are a colorblind woman there is some chance for your children to inherit it from you. But you shouldn’t be worried because color blindness does most often handicap your children not very much. And best of all, as you know how it feels you we will be able to perfectly help them out whenever they need it.

You can find more information about inheritance patterns of red-green color blindness at The Biology behind Red-Green Color Blindness.

6 Colors are Too Many for a Colorblind Guy

I always try to be smart when I use different colors to point out something. But it happens again and again that I still mix up the colors—even if I put together a good strategy.

This time it happened when coloring a simple graphics illustrating a project lifecycle model. It consists of six modules and therefore I was looking for six different colors for coloring them. And this was where the whole problem started.

How can I choose six different colors from a set of about twenty crayons, which I won’t mix up? The simple answer is: I can’t.

I really tried to find colors which are easily distinguishable even for my eyes. But with my color blindness this is almost impossible. I’ve chosen the following colors:

  • Blue
  • Yellow
  • Red
  • Violet
  • Orange
  • Green

I arranged them in the above order to be sure not to mix them up. The color pairs blue/violet, yellow/orange and red/green looked very close to each other for my colorblind eyes.

But of course it didn’t work. Suddenly I didn’t had the correct order anymore and it started to get problematic. So I didn’t color red and green right away, because they are the most problem colors for a red-green colorblind guy like me. I colored them only after my presentation, when there was more time to have a closer look at the crayons.

So everything was perfect now? Unfortunately not. I couldn’t believe it but someone else (with not color vision problem like me) did point out to me, that I colored two modules in blue…

How could I just mix up violet and blue? I used the wrong color again. Unbelievable but I just can’t distinguish six colors.

And what do I learn for the next time: Ask somebody else to do it for you.

The Man who Mistook his Wife for a Hat

A reader told me once, that there is a book by Oliver Sacks about Losing Color Vision called The Man Who Mistook His Wife For A Hat: And Other Clinical Tales. It shall include some story about a man with a form of acquired color blindness.

The Man Who Mistook His Wife For A Hat
The Man Who Mistook His Wife For A Hat

I’ve read it—and couldn’t find any word about this colorblind man. Am I now completely blind? Or did I just pick up a wrong edition of this book?

Anyway, the book includes many interesting stories about very special clinical cases. For example a man who can’t really see the big picture anymore. He sees just tiny little details and can’t put them together anymore like to a see a face. That’s why he mistakes his wife as a hat—a true story.

Despite the fact that The Man Who Mistook His Wife For A Hat by Oliver Sacks didn’t include a story about the colorblind man, it is still worth reading.

How to Explain Color Blindness to Your Little Boy

Often you won’t recognize if your little boy is colorblind or not until he goes to school or even later.

Sometimes—you might have color vision deficiency in your family or your child just can’t see certain things which stick out to you—you realize that he is colorblind in his early childhood.

We are pretty sure our two-year-old is red-green colorblind. My questions are:

  • How/when do I tell him, and what do I say?
  • What can we do to help him?
  • Can you recommend any books?

First of all I would like to mention that a two-year-old still has to learn all the colors and the correct naming. But it might also be true, that he can distinguish a whole set of colors and match them correctly except some of them. If this happens, what can and should you do?

When do you tell him? Definitely not today and not tomorrow. There is still enough time to learn more about color blindness and to learn together with him, how he can handle the colors. As he won’t really understand the concept you should wait until either, he realizes himself about his handicap and starts asking you about it. Or when he enters kindergarten/school, because colors are often used to symbolize and differentiate certain things.

How do you tell him? There are many different ways to go. You might like to find a friend of him which is also colorblind (every 12th boy is colorblind) as a support. Or point out strength and weaknesses of every family member. Everybody has a little handicap to carry around. As more as you know about color blindness before talking with him, the better you can answer his questions.

What do you say? Maybe you could start looking at a bush with red flowers from a distance he can’t see them. When walking closer, suddenly he will see them. And really close, he will also see the difference in color. Starting from there, you could tell him, that you could see those flowers already from the distance. You also have to tell him, that he relies more on brightness than on hues to distinguish colors—which makes him also a better brightness-differentiater.

What can you do to help him? Use patterns combined with colors to mark things, label his crayons, use well distinguishable colors for his cloths, watch out for color coded subway or bus maps and explain them to him. You can also help him, when you talk with his first teachers as they might not be aware of color blindness. Try to help them to understand his problems and what they can do to help him. And most important, don’t push it to far. He also has to and will learn how to handle it by himself.

Can you recommend any books? There are Arlene Evans Books About Color Blindness which should really help you and your son to understand color vision deficiency in more details.

If you also have some questions about color vision deficiency, don’t hesitate to ask me. Or you might like to subscribe to the RSS feed of Colblindor to get the latest news on any aspects of color blindness.