Category Archives: Academic

Free Lecture: Colour Assessment & Diagnosis Test

color-assessment-diagnosis-test-lectureThe Royal Aeronautical Society will be holding a Lecture in London on 28 September relating to Use of New Technologies and Therapies in Aviation Medicine.

One of the speakers is Dr Robert Hunter, Head of Aeromedical Section, CAA. He will be talking about the new Colour Assessment & Diagnosis Test.

The Colour Assessment and Diagnosis (CAD) test is a newly developed test for colour vision deficiency in pilots. The CAD test is completely sensitive and specific for the identification of normal colour vision and the test is able to accurately and repeatably quantify the degree of colour vision loss in individuals with colour vision deficiency.

The pass/fail criteria are based on the point at which the degree of deficiency degrades performance in critical piloting tasks, the most critical task being the interpretation of the Precision Approach Path Indicator (PAPI) lights. Using the pass/fail criteria that have been established, 35% of colour deficient pilots will be granted unrestricted class 1 medical certification.

The presentation describes the background to the work including current tests for colour vision deficiency, an analysis of colour critical piloting tasks, and the CAD test.

If you are around go and join this free lecture. You can find further information about this talk at the Royal Aeronautical Society Conferences homepage.

Do Blue Colorblind People Have More Sleep Disorders?

I was contacted by a phd student of the Flinders University, Adelaide. She is looking for people suffering from blue-blindness (tritan color vision defects) as this could be in relation to their sleep wake cycle.

Read more in the following sentences from Claire. And if you are interested, please contact her directly. I think it would be very interesting for all of us to learn more about this topic.

I am a new phd student starting out at Flinders University, Adelaide. I am also doing a medical degree too. It has been discovered that blue light is most effective in re-setting peoples circadium rhythm (sleep wake cycle). But exactly why and how is completely unknown.

The only way a definitive experiment could be done would be to see if someone who could not see blue could still have their circadium rhythm reset or not. It would be the first experiment of its kind because the condition is so rare. As well as publishing awareness of colour blindness, particularly rare forms, it may also lead to investigations of whether people who have defective blue photoreceptors are more likely to have sleep disorders.

The experiments are very simple. Basically the participants just have to wear a pair of glasses that shines some light into their eyes at a certain time of the day (e.g. in the morning for an allotted amount of time), then later saliva is taken to measure melatonin (indicator of circadium rhythm). No one had thought of doing it with colourblind people before, and the proffessor actually laughed at me and said it would be impossible to find anyone, anywhere with such colour blindness. But colour blindness is not as rare as people think, and I am on a mission to find them.

So anyone who could help or even just explain their condition to me would be so much appreciated. Please anyone contact me at walk0299[at], I would be so happy just for any information on your condition, and how it affects your life in general. I am looking forward to hearing from you.

Thank you so much – Claire

Claire, if you have any results ready, please let me know so I can share them with the readers of Colblindor.

Colorblind Colors of Confusion

When people hear that you are red-green colorblind, most of them think, that you can not distinguish between red and green. But that is wrong.

Of course, red and green are some of the problem colors when you are suffering from red-green color blindness. But…

  • … some shades of red and green are easily to distinguish,
  • … and many other colors also cause problems.

The following diagrams of the CIE 1931 color space can give you a quite good understanding of which colors are problematic for colorblind people.

Protan Lines

Deutan Lines

Tritan Lines

All colors in the direction of the lines might be hard to differentiate. There are three different diagrams corresponding to the three main color vision deficiencies: protanopia (red-blindness), deuteranopia (green-blindness), and tritanopia (blue-blindness).

Copunctal Point x y
Protan 0.747 0.253
Deutan 1.080 -0.800
Tritan 0.171 0.000

See Wyszecki & Stiles, Color Science (2nd ed.), 1982, Table 1 (5.14.2) p. 464

The lines shown above are called confusion lines and converge at a point which is called the copunctal point. For the three different types of color vision deficiency there are three different copunctal points.

For the two types of red-green color blindness (protanopia and deuteranopia) the main problem area of colors is really in the axis between red and green. And on this side of the color space, the confusion lines are quite the same for both types. This is why they are called red-green color vision deficiency. But on the left side of the diagram you can see that they are quite different confusion lines which show the problem colors.

If you would like to learn more about color matching and confusion lines you might like to read the article Color Matching and Color Discrimination by Joel Pokorny, a very well known researcher in the field of color vision deficiency.

As you can see from the above diagrams, the whole spectrum of colors is some way reduced for colorblind people. It is definitely not only red and green (protanopia/deuteranopia) or blue and yellow (tritanopia) which can not be distinguished.

If a Women is a Carrier of Color Blindness does she also Suffer from it?

Many people think that only men can be colorblind. As we can learn from genetics, this is not true. There are a lot more men colorblind, but also women can suffer from a color vision deficiency.

Here’s a question for experts: according to a vision test in a magazine she did recently, my mother has a slight red-green weakness, which, however, is hardly noticeable in daily life. Is this also colour blindness, although that is really rare in women, and it’s nothing compared to her father’s colour blindness, which was pretty severe? Or can it be due to her being a carrier?

On a first glance it looks like we can give a quick and short answer on this. But thinking about it, makes it a bit more complicated.

First of all, yes women can be colorblind and even if it is a very weak form of it you call it color vision deficiency (a wording which reflects much better the fact that colorblind people can also see colors). And it doesn’t matter if it is rare or not.

Sex chromosome X encodes color vision.
XY = man
XX = woman.

Now let’s have a closer look at this case. We have a colorblind man which means he has a defective X chromosome which pairs with a Y. The Y chromosomes have no coding of color vision and therefore have no important role here. His daughter will inherit this defective X and another X from her mother. We have now to possibilities:

  1. The mothers X is also defective concerning color vision.
  2. The daughter inherited an X encoding perfect color vision.

In the first case the daughter definitely shows some form of color blindness which she inherited from both of her parents. It is said that the weaker form either from her father or from her mother would control her color vision.

X-linked recessive carrier mother

According to genetics the daughter shouldn’t be colorblind in the second case. But it is known from different cases that this isn’t always so easy to tell. Up to now it is not fully understood how those two X chromosomes affect the color vision system. It could be very well that both of them play their part in the setup of the color receptors. In this case the strong color blindness encoded on her fathers X chromosome could also affect the color vision to a certain degree.

Putting this together means, that the daughter can show characteristics of color vision deficiency in the first and the second case. Only a detailed genetic analysis could tell us more details about it.

Can Color Blindness Cause Eye Pain?

Usually everybody talks about congenital color blindness—inherited through your parents.

But there are also many people who are suffering from acquired color vision deficiency which isn’t present from birth on and even could disappear again after a certain timespan.

Several days ago my boyfrined told me that his eyes started to hurt form time to time. He never had problems with the eyes. He is a web designer and a programmer though. This pain was increasing from day to day and yesterday the doctor told him that he has some type of Daltonism. He started to loose the real colors during dayperiod. He was told to get physical health and make exercises often.

I want to know is this possible? Can this be a real diagnoses and how can we help it?

It is definitely possible to loose color vision. This can be caused by many different diseases, some of them I’ll list below. Concerning this diagnosis the main question I would ask is:

Can any form of color blindness cause eye pain?

In this case you can compare it with near- or farsightedness. Some people have it, some not. Most people get farsighted when they get older but most important of all, it never causes pain. This is just what and how you can see, but it can never be the cause of pain. It might only be a symptom for some other disease.

This is the same with any type of color vision deficiency. It doesn’t matter if you acquire it or suffer from some congenital form, color blindness never causes any pain. In this case the described color vision problem is caused by something else. The color blindness itself is a side-effect of this and the pain must be caused by something different.

Here is a list of possible causes to loose color vision:

  • Diabetes, a disease in which you don’t produce or properly use insulin.
  • Injury. A strong hit on your head could make you loose color vision.
  • Age.. With age some changes in the eye can cause a blue-weakness.
  • Chemicals, Drugs and heavy Tobacco smoking.
  • Glaucoma

This list is not complete and there are many other diseases which can in certain cases cause color blindness.

Comparing the above description of eye pain and the list of diseases which could be a cause of loosing color vision, I would say it could be some form of Glaucoma. This is caused by an increasing pressure of the fluid inside the eyeball. There are many different forms of glaucoma, but some of them can cause eye pain and can develop enough pressure onto the blood vessels in the eye to cause some form of color vision deficiency.

The advice to get physical exercise sounds a bit strange to me but it could help (I’m not an eye specialist). Most important is, that color blindness doesn’t cause eye pain and therefore there must be something else causing the pain and with the side effect of loosing proper color vision.

I would strongly recommend you to contact an eye specialist to find the real reason behind the pain. He should be able to give you a proper diagnosis and hopefully can cure it.

You might also like to visit the Glaucoma Research Foundation, which provides a lot of very useful information and also offers help.

Monochromacy – Complete Color Blindness

A lot of people think, if you suffer from color blindness you can not see any colors at all apart from black, white, and shades of gray. But they are wrong.

This form of complete color blindness is a very rare subtype of color vision deficiency among much more common ones like the the well known red-green color blindness. You might say, in this case the wording color blindness isn’t chosen appropriate—and you’re right.

Colourful Bouquet
Colorful Bouquet
Grayshade Bouquet
Grayshade Bouquet

Color Blindness begins when you don’t have normal human vision which might be only a very light change of color perception. And it ends with complete color blindness combined under the umbrella term monochromacy.

If you are suffering under monochromacy, you perceive everything just in shades of gray. This makes it really hard to accomplish many everyday tasks, because colors are such a central part of our life. For example, people suffering form monochromacy might mix up the following colors:

  • green and blue
  • red and black
  • yellow and white

Monochromacy—also referred to as monochromatism—can be observed in different forms and even worse, many different names are in use:

  • rod monochromacy: typical or complete achromatopsia, total color blindness, day blindness
  • blue-cone monochromacy: S-cone monochromacy, incomplete achromatopsia
  • cone monochromacy: complete achromatopsia with normal visual acuity
  • cerebral achromatopsia: atypical achromatopsia

Before we dig a little deeper into the different forms of complete color blindness you should know the basics of vision and specially color vision.

The human eye has two different receptors inside the eye to perceive light. They are called photoreceptor cells. The rods are very sensitive on brightness and used for night vision. On the other side we have three different types of cones (trichromacy) which are responsible for colored day vision. The three different forms of cones have different peaks on color perception: red, green and blue. And the mixture of those three base colors makes us perceive such a huge variety of colors—or at least almost all of us. Compared to cones, rods play no role in color vision.

Rod Monochromacy

In this case your vision relies solely on the rods and the cones are usually not working at all. Some cases also report that the cones are absent, have some irregular distribution or that they show abnormal shapes. Occurrences are estimated to be between 1 : 30,000 and 1 : 50,000. But even if this numbers look very small, rod monochromacy is still by far the most common type of complete color blindness.

Rod monochromatism is often referred to as achromatopsia and is based on autosomal recessive inheritance. In other words, you need two defective chromosomes and it is equally distributed among men and women. Achromatopsia is characterized by the following symptoms:

  • complete inability to differentiate colors,
  • severe light sensitivity (photophobia),
  • long-sightedness,
  • involuntary eye movements (nystagmus),
  • and central depressed vision (scotoma).

Also rod monochromats are completely colorblind, they often learn to associate certain colors with objects and to differentiate some colors by their brightness.

Blue-Cone Monochromacy

This rare form of monochromatism is caused by loss or rearrangement of the genes encoding L- and M-cones. Because of that only blue color receptors (S-cones) and rods are transmitting color and/or brightness information. If you suffer S-cone monochromacy your are usually completely colorblind. But in twilight situations—where rods and S-cones are working—color perception can be compared with dichromatic vision.

There are reports about very different forms of blue-cone monochromacy and it is sometimes not easy to differentiate it from rod monochromacy. No exact number of incidences is available. Scientists estimate the frequency at 1 : 100,000—for men. Because red and green cones are encoded on the sex chromosome, inheritance patterns are similar to red-green color blindness. Occurrences in women are unknown.

Cone Monochromacy

Also known as complete achromatopsia, this form is very rare. Only a few cases have been reported and none of them is fully accepted. It is assumed that they are either have working L- or M-cones and inactive or absent S-cones. Compared to blue-cone or rod monochromacy, cone monochromacy doesn’t have reduced visual acuity or any special light sensitivity.

Cerebral Achromatopsia

In this case optical examinations show normally functioning cones and rods. It is not understood in detail yet, but it is thought that the color receptors are working properly only the information is not reaching the brain or is not processed. Only a few cases have been investigated. Cerebral achromatopsia is unlike the other types of monochromacy not inherited but and acquired color vision defect. It may be caused by trauma or illness.

The academical background and many references on all types of monochromacy can be found in Opsin genes, cone photopigments, color vision, and color blindness by Sharpe et al. An internet information portal on achromatopsia is provided by the The Achromatopsia Network.

Can I bee Slightly Colorblind?

If you are colorblind it is not just about being colorblind or not. There are many different types and characteristics of color vision deficiency which you can suffer from. Color blindness is an umbrella term for all those different forms—and not even a good one.

I’m 13 years old and have been told I am red-green colour blind but only slightly. I have done research and taken MANY colour blind tests. But I’m still confused because how can I be slightly colour blind? Either I am or I am not. I have failed most of the tests I have taken and my optician has told me I am slightly colour blind towards red-green (the most common) but want to know how I am only slightly colour blind and what the scientific word for being slightly red-green colour blind.

First of all, you shouldn’t rely on the color blindness tests available online. These tests are just used to give you a feeling what kind of color blindness you are suffering from and how severe it is. But because every computer display can have different color adjustments they are not 100% reliable.

This young reader says, that either you are colorblind or you are not. This is true and false. If you go to your eye specialist and take a color blindness test, he will tell you if you have normal color vision or not. So yes, either you are colorblind or not.

But he can also tell you, what type of color blindness you are suffering from and the approximate severity of it. There is a whole terminology of color vision deficiency which I don’t wont to list here on the whole. Just the most important facts.

  • Types of color blindness:
    • Red-green colorblind: This is the most common form and according to its name, causes the biggest problems with red and green. There are two different subtypes: Red-blind (or -weak) and green-blind (or -weak).
    • Blue-yellow colorblind: This type of color vision deficiency is not so often seen and actually the colors blue and green (not yellow) are the problem area.
    • Completely colorblind: A very uncommon type which makes you see only in shades of gray. Unfortunately a lot of people think that every colorblind person can only see in shades of gray.
  • Severity of color blindness:
    • Anomalous trichromat: You have still three different types of color receptors as someone with normal color vision. But one of them is slightly shifted in its peak of sensitivity and therefore you can’t see the same broad color spectrum as others.
    • Dichromat: Here only two of three color receptors (cones) are working. You have to mix your perceived color just with two signals compared to three with normal color vision. The color spectrum is strongly reduced.
    • Monochromat: Either no color receptors are working (rod-monochromacy) or just one of them (blue-cone monochromcy). Anyway you will have either just grayscale vision or a very very restricted color vision.

This means, that is possible to suffer from any possible severity of color blindness. This because the three different color receptors have a highest peak of sensitivity. With an anomalous trichromacy, one of those peaks is shifted towards another one; usually the red peak towards the green or vice versa.

Because of that shift and the resulting peaks which are closer to each other, less information is available to mix up the final color in your brain. And this makes you either slightly colorblind (peaks still far apart) or more severely colorblind (peaks coming closer).

The academic term for a slight red-green color blindness is either protanomly (red-weakness) or deuteranomaly (green-weakness). Both types are a subtype of red-green color blindness and a form of anomalous trichromacy.

19th Symposium of the International Colour Vision Society

The International Colour Vision Society (ICVS) is an international group of physiologists, psychologists, physicists, geneticists, optometrists, ophthalmologists and others who have a research interest in the many aspects of colour vision and colour vision deficiencies.

ICVS Symposium

This group will hold its 19th Symposium of the International Colour Vision Society from July 27 to 31 in Belém, Brazil.

Here is an introductory excerpt of the Program Book on this years symposium.

A glance at the program reveals that the traditional interests of our Society are well represented this year, including contributions by physiologists, psychologists, physicists, geneticists, optometrists, ophthalmologists, and other related professionals who have a research interest in the many aspects of colour vision and colour vision deficiencies. One special session is dedicated to the Nagel Centennial, the anniversary of the introduction of the W.A. Nagel Anomaloscope in 1907.

The program includes in impressive list of speeches with many topics directly related to color blindness. I’ve chosen some of them in the list below to give you an impression of actual research topics.

  • Welcome to the wonderful world of color: Gene therapy treatment for colorblindness.
  • The effects of colored lenses on the number of discernible colors perceived by dichromats in natural scenes.
  • Surface color perception of color defective observers under dim illuminations.
  • Performance of the Lanthony New Color Test by young children.
  • Mass screening for color-vision deficiencies in Norwegian children.
  • Color deficiency correction – methodology and experiment report.
  • The contribution to Rayleigh matches of the third red-green photopigment of color-defect carriers.

As described above it is also the centennial of the Nagel anomaloscope, which was introduced in 1907. The Nagel anomaloscope was introduced to measure severity and type of red-green color blindness. It is since then the reference on color blindness tests and of course evolved along the way to cover different types of color blindness.

Maybe we will have the chance to get a grasp of some of the speeches and catch a fresh breeze of academical research on color vision deficiency. Stay tuned.

16 Essential Questions about Color Blindness

Courtney is doing a Graduation Project on the topic Color Blindness and was asking me for some help. She put together a list of 16 questions about color vision deficiency which I would like to answer hereafter.

Actually not all of the 16 questions are on the topic of color blindness. We are starting with some simple questions about myself. But after that we are heading right into some fundamental topics. And with each question going deeper into more details, after reading through all of them, you will have quite a good overall picture about color blindness.

  1. What is your name?
    Daniel Flueck. (Actually it’s written with two points above the u and without the e afterwards: Flück. But this is my international standardized name :-)
  2. What is your field of work?
    I’m working in the IT education, which means my day to day job has nothing to do with my engagement for this weblog about color blindness. It’s only the interest into the topic and my own color blindness which drives me to put together some hopefully useful informations.
  3. Do you have to be licensed or certified to perform your work? What is the license called?
    For my job; not really. But as I wrote above, my job has nothing to do with color blindness. And for my weblog writing I also don’t own a licence yet ;-)
  4. What is your educational background?
    I have a masters degree in mathematics. Again something completely different. Sorry for that. But starting with the next questions I can hopefully give you some more satisfying and accurate answers.
  5. What is color blindness?
    Color blindness is a biological condition, where you can’t distinguish the same broad spectrum of colors as somebody with normal color vision. The term stands for anything between almost normal color vision and the most pronounced form, where you can only differentiate shades of gray.
  6. Who is mainly color blind, males or females?
    Mainly males suffer from color vision deficiency. This is because the most common form of color blindness is provoked by some variations on the X chromosome—also called sex chromosome. Because women have two such chromosomes, they have the chance to overmodulate the defective one. On the other side, men have only one X combined with a Y chromosome and therefore suffer more often form color blindness.
  7. How do you know you are color blind?
    My family found out about my color blindness when I was in kindergarten and painted a sky in a nice pink. They also were aware of color blindness because my father also suffers a mild form of it. Only when I was twenty years old I did a simple check up at the ophthalmologist to get it confirmed.
  8. How does an optician or an ophthalmologist test for color blindness?
    Actually I really don’t know. But I fear that most of the time they only have some Ishihara plates to test colorblind persons. For proper testing you also would need some other tests like an University test for blue-yellow color blindness and of course an anomaloscope to get an accurate test on red-green color blindness.
  9. At what age should people be tested for their ability to see colors?
    Parents should be aware of color blindness specially with boys, because almost 10% of all men have some type of color vision deficiency. If you think that there could be a problem you might test it in kindergarten, because if you know about it, you and the teachers can give better support to your child. On the other side if you are not sure how good your color vision is, you can test it before you decide on your later profession, because there could arise some major problems.
  10. Is there a reason that color blindness is important to diagnose? Why?
    First of all, I don’t think it should be tested in general. Only if you have some concerns a test can help you very much to classify them. It is important to diagnose color blindness, because only then you can take proper precautions to help for example your child with homework.
  11. What tests do you go through to find out if you are colorblind or not?
    There are many different tests for color blindness. Some of them are based on images, others need a special equipment and today you even have some computer based tests. It’s always good to use different tests for an exact diagnosis. The most famous color blindness tests are the Ishihara plates, many colorful dots showing a number in an other color which is not visible for a colorblind person, or the anomaloscope, where you have to adjust a mixture of red and green to the brightness of yellow.
  12. Are there treatments to cure color blindness?
    No, there are no treatments for any color vision deficiency. There are some lenses, which try to enhance the color vision but otherwise you just have to get around with it. Maybe in the future there will be some possibilities in genetic manipulations, but there is still a very long way to go.
  13. Is there a cure for color blindness?
    For most people suffering from color blindness there is no cure. But there are some forms of acquired color blindness: A hard hit on the back of your head can cause blue-yellow color blindness. With this type of acquired color vision deficiency there is a chance that normal vision will come back after some time. But again, there is no treatment to enforce it. You just have to wait and hope for the best.
  14. Are you aware of any specific jobs that color-blind people could not perform?
    The most talked about job which can not be taken by a colorblind person is pilot. Because pilots have a big responsibility and almost everything in a cockpit and outside works with some color coded signals, it wouldn’t be a good choice of job if you have some kind of color vision deficiency. There are also problems to apply for police officer, and you might have some disadvantages in biology/chemistry and as an electrician, because of color coded wires.
  15. How does color-blindness interfere with the performance of those jobs?
    Some jobs like pilot just can’t be done and that’s ok. In other jobs a colorblind person will have some handicaps which have to be overcome with creative solutions. You might need some extra help on colors from your workmates to accomplish certain tasks. But every colorblind person will find out himself, if a job can be done as desired and if the chosen job is the right one concerning their deficiency.
  16. Is color-blindness a genetically inheritable trait?
    By far the most cases of color blindness are inherited from a mother to her children, and not as often thought from a father to his son. But there are some possiblities of acquired color vision deficiencies. Aging, heavy alcool consum, toxic ingredients, some eye diseases and even a hard hit on your back head can also cause color blindness to a certain degree. If you are suffering from such an acquierd form, you wan’t pass it on to your children. Therefore color blindness is not in all cases a genetically inheritable trait.

If you like to get some more information on certain topics you can follow some of the links below.

I tried to put together some short and accurate answers. Browsing through Colblindor, you will find some more detailed answers on many topics discussed above. If you like to get updated on the latest issues about color blindness, you can subscribe to my RSS feed.