Color vision deficiency is a very common disease—specially among men. So there have to be also many colorblind doctors and health professionals. Do you know if your medic is colorblind? And what if he really is, did he take some wrong decisions because of his color blindness?

Perfect or good color vision is not yet a precondition for any medical jobs. And there aren’t many studies about color vision deficiency and how it affects medical skills. J. Anthonny Spalding did a research on exactly this topic about ten years ago and brought together some interesting and still newsworthy results. He called his paper Colour vision deficiency in the medical profession.

Several studies in the last century have shown, that color vision deficiencies are occurring at about the same rate for doctors as for the population at large. In one of those studies, colorblind doctors were asked about their most common problems caused by their color vision deficiency:

body color changes of pallor, cyanosis, jaundice, and cherry red
rashes and erythema of skin
charts, slides, prints, and codes
test-strips for blood and urine
ophthalmoscopy
blood or bile in urine, faeces, sputum, or vomit
otoscopy

This is a quite impressive list of diseases which could be wrongly diagnosed or overseen by a colorblind doctor. If they know about their color vision deficiency—not every doctor knows about it—they try to overcome it by closer observation, asking others, and paying more attention to the patients medical history.

By taking greater care and the fact, that there are many diagnosis not involving colors, it is widely accepted that your colorblind doctor performs as well as a non-colorblind medic. There are also not really any serious errors known based on a misjudgment of a doctor suffering from a color vision deficiency.

But still, there are some situations where color blindness could be the cause for wrong decisions:

If a single sign of observation is essential to take the correct action.
Scanning of an area for the detection of small features (bacilli, rash,…).
Special work conditions like speed, alone, and poor illumination.

Dr Spalding concludes, that all this points to the need for screening for color vision deficiency for medical students and doctors. Which could specially be used for better counseling and an informed choice of career. But he also believes, that because of the wide range of specialties, the question of non-acceptance of applicants to medical school need hardly arise.

Probability of Color Blindness

April 15, 2008

@colblindor

People No Comments

It is well known, that approximately every twelfth man and every 200st woman suffers from some form of color blindness. But what about some real life probability numbers concerning color vision deficiency?

What’s the Chance of Color Blindness?

If you are a teacher you might ask yourself:
What is the probability that one of my pupils is colorblind?

And what about the chance to have a color vision deficient pupil
if you have only boys in your class?

Your son is maybe colorblind and joining the kindergarten pretty soon.
How big is the chance, that there is another colorblind child in his class?

…and he might also play in a soccer team.
Will he be the only colorblind boy in the team?

Are you a football coach? What is the probability that
one of your players from a team of 33 has a color vision deficiency?

Or you are leading at work a team of eight persons.
What’s the chance, that you have a colorblind person in your team?

Let’s say you know 100 persons. The probability that one of them
is colorblind has to be pretty high. But how high is it really?

In general, if two people meet, how big is the chance
that they are both suffering from color vision deficiency?

Before I will reveal the answers to the questions above or before you can compute it yourself, you need some more input. To calculate probabilities certain assumptions—like a base probability of color blindness or a class size—have to be taken. The results below are therefore based on the following numbers:

Probability of color blindness in men: 8%
Probability of color blindness in women: 0.5%
Average class size: 20 pupils
Group line-up: 50% male – 50% female

Based on this assumptions I calculated the following probabilities of color vision deficiency. Hover over the letters to see the results. But before viewing them, why don’t you try to answer the questions yourself? Just take a guess and have a look how close you can get to the real probabilities of color blindness.

58% 81% 54% 57% 94% 29% 98.7% 0.18%

And in other words:

Almost every teacher or trainer has a colorblind pupil or team member.
If you are colorblind pupil, there is a big chance that there is another colorblind child in your class.
You can almost be sure that you have at least one colorblind friend.
Approximately every 500st handshake is between two colorblind persons.

If you have any further questions, don’t hesitate to contact me or just write a comment on this article.

Improving Color Vision with Lenses for the Colorblind

March 29, 2008

@colblindor

Tools 120 Comments

Every person suffering from color vision deficiency has the same dream: I would like to see the world as everyone else can and I would like to be able to name colors correctly. Color correcting lenses claim to make this dream come true.

The History of Correcting Color Vision

It is said that already in 1837 a German scientist called Seebeck was writing about the possibility to correct color vision deficiency with some sort of lenses. But only in the twentieth century many people investigated and developed different types of tinted lenses and glasses which should help colorblind people to improve their vision.

Many people thought that you really can correct a color vision deficiency and turn it into normal vision. As of today it is well known, that color blindness is in most cases a genetic defect which can’t be corrected except with not yet existent genetic manipulation.

The System of Lenses Enhancing Color Perception

How does it work? It is actually very simple. You just use a tinted lens in one of your eyes, usually in your non dominant eye, and that’s it. In this case both eyes actually see different colors and because of that the brain can extract some other information out of certain colors. You can also use two different tints in each of your eyes. This depends very much on ones personal impression. But it definitely won’t work if you use the same colored lenses in both eyes.

This works for all types of color blindness (protanopia, deuteranopia, tritanopia) in the whole range of severities, with one exception. If you suffer from a complete color blindness (achromatopsia) there is currently no system which can give you back color vision.

The Things You Should Know about Improving Color Vision

First of all you can’t really improve color vision, you can only let’s say adjust your color sensation. The manufacturers claim that you can pass Ishihara plates tests without any errors when using such lenses. And that might be true. But this doesn’t mean that your overall color perception is enhanced. You will also loose some of your color perception in another area of the color spectrum.

Facts You
Should Know

Here are some of the main handicaps when you are using tinted lenses to improve your color vision:

The performance on Ishihara plate tests improves a lot. But in contrary there is no significant improvement in lantern tests and in color arrangement tests.
Color perception improves in your problem area like red-green but at the expense of an increase in blue-yellow confusion.
Most people experience difficulties in dim light or at night when wearing color correcting lenses.
You might experience some distracting effects like lustre, fluorescence, 3-dimensional effects, judgment of distance and motion.

But most important: Don’t wear them for driving! If you come into dim light situations like a tunnel you might have some problems with judgment of distance or motion which isn’t safe for driving.

The Results of a Scientific Study about Color Correcting Lenses

In 2000 a group of four scientists of the University of New South Wales, Sydney, tested the ChromaGen contact lens system trying to find out if they can enhance color perception for colorblind people. Fourteen persons suffering from red-green color blindness were involved to test the efficacy in standard color blindness tests, and to evaluate subjective performance in the “real world” over a 2-week lens-wearing period.

Lens tints are available in seven hues (magenta, pink, violet, yellow, aqua, orange and green), and most tints are available at light, medium and dark densities. Most often the pink lens in its darkest density was felt to enhance color perception at the most. Second ranked was the magenta lens, also in the darkest density.

I already included some of the results of this study in the sections above. To me there are two more results which I would like to pass on to you. This might give you a better feeling, if such color enhancing lenses are something for you or not.

A. Would you
pay the price?

At the end of the two week lens-wearing period the people joining the test were asked whether they would be prepared to pay full cost of the lens, which is around $500 per lens. Only two out of 13 would be willing to meet this cost. One of them was really enthusiastic about them and the other one could use them very well on his job as a casino employee.

B. Would you
wear the lens?

One of the persons even returned the lenses, it was too much bother for him. The others expressed interest in wearing them on an occasional basis, maybe once or twice a week. For some of persons the disadvantages of lens wear just outweighed the benefits of them.

The Vendors of Color Correction Lenses

I suppose there are many different vendors all around the world. The following three are the most established ones:

ColorMax from Dr. Thomas Azman who developed the ColorCorrection System, a unique system of tests and filters for a systematic approach to color vision correction. (Based in Maryland, USA)
ColorView spectacle lenses help people with congenital red-green color deficiency to distinguish colors easier and reduce color confusion. (California, USA)
ChromaGen is a unique product that was developed to help patients who suffer from color deficiency. This product was used in the scientific study cited above. (United Kingdom)
Colorlite is also a leader in color vision diagnostic and correction. (Hungary)

Some products are available at certain optometrists all around the world.

Unfortunately I think that the dream of seeing colors as a colorblind person doesn’t come true. At least not with products like lenses which enhance color vision. They can get you a better color perception but I think the handicaps outweighed the benefits.

The New York Times also wrote an article about lenses which can enhance color vision at A New Technology That Colors the World (Sort of).

RGB Anomaloscope Color Blindness Test

March 11, 2008

@colblindor

Tests 14 Comments

The anomaloscope is the most accurate tool to classify your color blindness. Since it was developed by a German ophthalmologist just over 100 years ago it is used all over the world to check the severity of ones color vision deficiency and its specific subtype.

The classical anomaloscope is used to identify red-green color blindness. It consists of two different light sources which have to be matched. One source is a yellow lamp which can be adjusted in its brightness. The other one is made by a mixture of a red and a green lamp, whereas the mixture between those two colors can be calibrated.

According to the match the tool can tell you details about the following facts of your color blindness:

Red- vs. green-blindness,
dichromacy vs. anomalous trichromacy,
and the severity of your color vision deficiency,

As this tool is only available as a quite expensive equipment I tried to simulate it online. I knew that there is only a little chance to get the same results as the real anomaloscope. But I tried it anyway and designed the RGB Anomaloscope. As all computer displays are based on the colors red, green, and blue, it will always be a simple approximation of the real test.

The diagram below shows the test results as matching-lines of some red-green colorblind persons. Each point means that this person matched a certain red-green combination to some shade of yellow. Non-colorblind people would only match the point 50/50 with some variances.

Unfortunately the results didn’t turn out as I thought. I couldn’t find any split between red- and green-blind persons. Also it isn’t that easy to judge the severity of a red-green color blindness.

Anyway, the test is online and you are welcome to try it out. Maybe there will be some improvements in future releases of the RGB Anomaloscope Color Blindness Test, so stay tuned.

A big thanks to everybody who helped me to develop the test.

New Color Blindness Test – Looking for Red-Green Colorblind Test Persons

February 10, 2008

@colblindor

Tests 3 Comments

The anomaloscope is the most precise instrument when it comes to analyzing red-green color blindness. It was developed about 100 years ago and is still in use all over the world.

An anomaloscope is based on two different light sources which have to be brought to a match. You can match them by adjusting either the brightness of a certain yellow color or the proportion of mixture between a green and a red light. According to the matches you can make the eye specialist can give you detailed information about the severity and subtype of your red-green color blindness.

The RGB anomaloscope uses exactly the same approach but as an online tool. But because computer displays are solely build up from the three main colors red, green, and blue, the results can’t be just transformed to this online color blindness test. And that’s why I need you.

I’m looking for red-green colorblind persons who would like to help me to develop the RGB anomaloscope color blindness test. The test is now online available as RGB Anomaloscope Color Blindness Test.

What do you have to do? Simply use the anomaloscope, that’s all. If possible you can take the test under different light conditions and using different computers. This increases the chance to get an accurate color blindness test in the end. And—of course—you have to be red-green colorblind yourself.

RGB Anomaloscope Diagram — Color Blindness Test
Results Diagram

On the left side you can see my test results. Every dot represents a color match. As I’m strongly red-blind the matching area spans the whole possible spectrum.

If you would like to join and help me to develop this new online color blindness test just contact me. Please write me also about the subtype and severity of your red-green color blindness—as good as you know. You can check this at Which Type of Red-Green Color Blindness is It? After contacting me I will send you the link to the tool and the password to get in.

And please be aware we might not get the results which I would like to see. So maybe I can’t give you any better results than the ones you already have.

Colour Blindness: Causes and Effects

February 8, 2008

@colblindor

Publications 6 Comments

The book Colour Blindness: Causes and Effects was written by Donald McIntyre in 2002. It is a great introduction for the general reader into the topic of color vision and its deficiencies, and discusses many different topics related to color blindness.

Donald McIntyre is colorblind himself and was in contact with many people doing research into color vision and color vision deficiences while writing this book. He compiled an excellent overview with many up to date details about the latest findings in the field of color vision deficiency.

The book is split into two equal parts, starting with the basics of color vision in the first part: The causes of Color Blindness. This part also includes a detailed overview of the different types of color vision deficiency and descriptions of some color blindness tests, which can be used to identify and classify your specific deficiency.

In part 2: The effects of Colour Blindness, McIntyre asked himself: “What is it like to be colorblind?” He researched different areas and has some answers ready for you, fitting into the following four chapters:

The appearance of colours: including a discussion and samples of how colorblind people see the world.
Everyday life: about art, sport, food and more, and the awareness of a color vision deficiency.
Careers: a great overview with some detailed information on professions and their suitability to color blindness.
Techniques that may help: like the Seekey or colored contact lenses.

There is one point concerning the book which I think could have be done much better: The Bibliography. The book provides a huge source of detailed information on almost every topic attached to color blindness. But when it comes to the sources of those information the author fails. In a book which acts like a well prepared aggregation I’m also expecting a very comprehensive list of sources to get deeper information if I would like to learn more about a specific topic.

Overall Colour Blindness: Causes and Effects is a great and easy readable book about color vision deficiency which I recommend everybody interested in the topic. Not only if you are colorblind yourself, but it can also be a great source of information for parents, spouses or teachers.

You can also visit the books homepage at www.daltonism.org.uk.

How Many Colors Can You Name in Five Minutes?

February 1, 2008

@colblindor

Tools No Comments

I suppose I could have done much better in this quiz, if I would have checked my own tool Color Name & Hue before I tried my best.

And I guarantee you, if you remember just a bunch of the 1640 different color names which are listed in Color Name & Hue, you’ll perform much better than me.

I just tried the How Many Countries Can You Name in Five Minutes and did much better. In the end they counted 43—and 227 remaining…

Color Vision Guide – A Fact Sheet on Color Blindness

January 29, 2008

@colblindor

Publications 1 Comment

The Color Vision Guide gives you a brief introduction to color blindness on a single sheet of paper. You could also call it a perfect starter for anybody interested in the topic of color vision deficiency.

About 14 years ago John Nash together with his brother and their mother created a guide to educate people about color blindness. He is suffering from green-weakness (deuteranomaly) himself and wanted to share his knowledge with others.

The guide includes the following parts, putting together a well designed sheet of information on color blindness:

Biological background of color vision and its diseases.
Jobs and color blindness.
The inheritance pattern of red-green color blindness.
Distribution diagrams of the three different color vision deficiencies.

On top of that the Color Vision Guide includes a small set of Ishihara color blindness test plates, which can be used as a basic check for red-green color vision deficiency. Well done.

John is also writing about different aspects of color blindness on his recently created weblog at the Color Vision Store. If you visit him, say hello from Daniel :-)

The Ishihara Unicorn Shirt

January 18, 2008

@colblindor

Children 3 Comments

Last December Nick offered 50 free shirts with an imprinted Ishihara like unicorn image. They were all given away to colorblind children for free.

He was so kind to send me also two of them for my two little toddlers. As you can see, the shirt is still a little bit to large for my boy.

I showed the shirt to my son and asked him: “What do you see?” His answer was of course: “A horse.” What else dad?

If I look at the image I can see only trees—and a lot of dots. Thanks Nick.

Does Color Blindness Disqualify from being a Firefighter?

January 15, 2008

@colblindor

Professions 12 Comments

It is quite well known that a lot of police officer applicants are disqualified by their color blindness. But what about if you would like to become a firefighter and you have a color vision deficiency? Do the same rules apply?

I’ll share my thoughts with you after the following personal story I received by a reader of Colblindor.

I’ll give you a bit of history on myself. I have recently taken schooling to become a firefighter, and seem to have run into a wall due to a color deficiency which I have. Funny things is I went to an ophthalmologist about 2 years ago and was cleared for the D-15 test with 0 errors.

But the next time I took it I convinced myself that it was suppose start with blue and end in green as the doctor did not say it was to fade into red. For some reason thats what I thought it was the last time I took, while I was doing it though I knew it was incorrect. When the doctor pulled it from me obviously it was horribly wrong. So he sent me for further testing during which i did D-100 plus lantern. The D-100 I used one eye at a time and it was difficult. End result I have been diagnosed with severe color blindness. And yet I can do the D-15 online with 0 errors and the confusion test with decent results as well as 1 wrong in ten.

Wondering where you might recommend getting some solid answers as there seems to be a lot of ignorance in the medical field and the fire department. I went through fire school with no problem, as well as the rest of the courses I took with no problems what so ever, and now they tell me that my colorblindness is a hazard. Anyway, right now I am quite frustrated and looking for answers as this is what I want to do—yet I feel that I being discriminated based on ignorance of color blindness.

Now this sounds pretty unfair. You accomplish everything just perfectly and only your color blindness should disqualify you to become a firefighter?

Has color any importance for firefighters?

As you know every fire has its color or better said consists of a whole range of colors. The colors not only tell us something about the burning substance but also are very closely related to the heat of a fire. For example a red fire can have a temperature between 977°F (525 °C) with a just visible red and 1830 °F (1000 °C), a cherry, clear red.

Also smoke has a color which can tell you a lot about the elements making up the smoke you see. And as any smoke can be very heavily toxic it is important to be able to distinguish different shades of color. At different stages of a fire the smoke color changes and therefore it is important for a firefighter to be able to interpret colors appropriately.

This are only two reasons why good color vision can help you to be a professional firefighter.

How firefighter applicants are tested for color blindness.

Often a standard test will be used to test if you have good color vision or not. Some type of Ishihara plates are very well known and often used. But you could also come across any type of arrangement test or a simple lantern test.

If you look at the following recruitment information of three different Fire and Rescue Services, you will see that it is very common to ask for good color vision. But the rules for color blindness can differ between the recruitment centers.

Hampshire Fire and Rescue Service
The minimum standard accepted by HFRS is the Farnsworth D-15 standard test.
Shropshire Fire and Rescue Service
You must have an appropriate level of colour perception, if you are found to be colour blind, we will send you for more tests to determine if you can work safely in a safety critical environment.
Devon and Somerset Fire and Rescue Service
Potential firefighters are subject to certain entry requirements specified by law. Applicants should be aged 18 and over; have good eyesight, not suffer from colour blindness.

NFPA: color vision deficiency doesn’t disqualify you

In the latest edition of the Standard on Comprehensive Occupational Medical Program for Fire Departments (2007 Edition) published by the National Fire Protection Association the rules concerning color blindness have changed. The following Report on Proposals makes it clear, that a color vision deficiency doesn’t disqualify you anymore from being a firefighter.

Formerly, color vision deficiency was listed as a Category B* medical condition. However, it is felt that within most cases this condition will not affect the ability of a member to safely perform the essential functions of his or her job. The fire service physician should consider the color vision deficiency of the individual and consider the color vision requirements of the member’s job and reach an individual determination.

*Category B: A medical condition that, based on its severity or degree, could preclude a person from performing as a member in training or emergency operation environment by presenting a significant risk to the safety and health of the person or others.

How to apply as colorblind firefighter

First of all you shouldn’t just forget about becoming a firefighter just because you have any kind of color blindness. As written above there are many different rules used and views are changing for the benefit of colorblind applicants.

So if you apply just be honest and tell them the truth about your vision. It won’t help you if you try to hide it or cheat on certain tests, because most often it will strike back and you will be looked at as an unreliable person. I would tell them about your color vision deficiency from the first moment on.

Then you can take the test and see what happens. If you pass, that’s perfect. And if you fail and they won’t let you go one step further just because of your color blindness, you should ask for precise explanations and try to describe them, how you see the world and how this could handicap your work as a firefighter.

Of course it could help you if you tell them about the most recent NFPA Report 1582 (see above) and their changed view on color blindness.

Maybe discussing color blindness at FirefighterNation.com, or other places, could also help to get the topic of color vision deficiency more recognized at recruitment offices, which will help all colorblind colleagues which would like to become a firefighter.

Fire! Picture taken by Wili Hybrid.