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 good 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:

1. If a single sign of observation is essential to take the correct action.
2. Scanning of an area for the detection of small features (bacilli, rash,…).
3. 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.

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:

1. Probability of color blindness in men: 8%
2. Probability of color blindness in women: 0.5%
3. Average class size: 20 pupils
4. 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.

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.

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.

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.

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).

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.

RGB Anomaloscope Test Results Diagram

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.

RGB Anomaloscope

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.

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.