Color Assessment & Diagnosis Test

Because of the lack of reliable, standardised tests and the absence of information on the specific colour vision needs of professional flight crew, the UK Civil Aviation Authority supported by the US Federal Aviation Administration initiated this study.

A team around Prof Barbur from the Applied Vision Research Center in London was mandated to find the minimum color vision requirements for modern flight crew, and a new color assessment and diagnosis test. This was the last part of the study after The Use of Colour Signals and the Assessment of Colour Vision Requirements in Aviation and a Task Analysis which included two operating case studies: the Airbus A321 and Boeing 757.

Dr Sally Evans, Chief Medical Officer at the CAA, says:

“The current diversity in colour vision testing methods and standards demonstrates the need to adopt more objective assessment techniques internationally. If the assessment methods and limits derived from this study were applied as minimum requirements for professional flight crew, 35 per cent of colour deficient applicants would be eligible for medical certification as a professional pilot. The CAA intends to promote this research internationally with a view to gaining acceptance of the CAD test and its incorporation in world-wide medical standards for pilots.”

This sounds very promising for all colorblind pilot applicants! So let us have a closer look at what this new color blindness test is all about and how they reached this new results.

Color Assessment & Diagnosis Test

The current procedures within JAA for pilot applicants are unsatisfactory for at least two reasons.

1. There is no guarantee that the deutan subjects that pass secondary tests can cope with safety-critical, color-related tasks, since the severity of their color vision loss remains unquantified.
2. Many color deficient subjects that can carry out such tasks safely fail the lantern tests and will not therefore be allowed to fly.

This findings and many detailed studies on color vision deficiency resulted in a new color blindness test, the color assessment & diagnosis test (CAD test). The subject’s task is to report the direction of motion of a colored square on a gray square background with dynamic luminance contrast noise. This new developed color vision test has shown in a broad study to be very accurate in identifying type and severity of one’s color blindness.

The subject’s color vision severity is measured in Standard Normal units (SN units). If your result would show a red-green threshold of 2 SN units this would mean, that you need a twice as strong color signal compared to a average standard CAD observer. This threshold can be quit different for deuteranomalous and protanomalous observers as a limit to pass the PAPI test. Details on this are shown in the conclusions.

PAPI Test

The Precision Approach Path Indicator (PAPI) was indicated as the most important, safety-critical task that relies largely on color vision. On this basis a PAPI simulator test was developed to quantify the severity of a pilots color vision deficiency which is still safe to fly. This simulator can be used in controlled laboratory environments.

PAPI Test Simulator

The simulator reproduces both the photometric and the angular subtense of the real lights under demanding viewing conditions when the lights are viewed against a dark background. Since other color-related tasks such as seeing the color of the parking lights or the discrimination of runway, center-line, red and white lights are less demanding, it is assumed that the pilot will also be able to perform correctly these tasks.

The aim was to identify type and severity of color vision deficiency which cause problems with the PAPI test and correlate those results to the CAD test results. In principle, this approach should make it possible to recommend pass/fail limits based on the observer’s ability to carry out the most safety-critical and demanding PAPI task.

Principal conclusions

The very promising results suggest that subjects with minimum color blindness that does not exceed 6 SN units for deuteranomalous observers and 12 SN units for protanomalous observers perform the PAPI test as well as normal trichromats. If these findings were adopted as pass/fail limits for pilots ~35% of color deficient applicants would be classed as safe to fly.

• When the ambient level of light adaptation is adequate, normal aging does not affect significantly either red-green or yellow-blue thresholds below 60 yrs of age.
• Analysis of PAPI results shows that the use of a modified white light results in significant, overall improvements in PAPI performance.The modified white is achieved simply by adding a color correction filter.
• 43 of the 77 deuteranomalous subjects failed the PAPI test. 29 out of the remaining 34 subjects that passed the PAPI test had CAD thresholds < 6 SN units.
• 20 of the 40 protanomalous subjects failed the PAPI test. 13 out of the remaining 20 subjects that passed the PAPI test had CAD thresholds < 12 SN units.

The study also concluded that the administration of the CAD test eliminates the need to use any other primary or secondary tests. When one includes normal trichromats, ~94% of all applicants will pass the so called fast-CAD screening test and be classified as safe to fly. This process is very efficient since the fast-CAD test is simple to carry out and takes less than 30 seconds to complete.

Official CAA news:
CAA research paves the way for more people with CVD to become pilots
CAA Paper 2009/04:
Minimum Colour Vision Requirements for Professional Flight Crew

Jay Neitz from the Neitz Color Vision Lab could just recently cure some colorblind monkeys and also developed a genetic color vision test. Building upon this basis in this new partnership they want to develop a new standard for color blindness tests and possibly have a breakthrough in curing color deficient patients.

Matt Lemelin, the founder and CEO of Genevolve:

“Our goal is to establish a new world standard for color vision testing and to increase public safety while providing a diagnosis that doctors may discuss with their patients. With this process, we can now diagnose the type of colorblindness and the extent of deficiency with amazing accuracy and precision.”

Lemelin also lists some of the reasons, why such a genetic color blindness test is a need today:

• Age: Todays color blindness tests often require a minimal age of at least 5 years. This could potentially affect a child’s development.
• Memorizing: Persons can memorize a test and alter the result. This could be very dangerous for some specific jobs.

I personally believe that a genetic test is only needed because people themselves want to have something fool-prove. A test which tells them the truth about their color vision, which is not influenced by some doctors judgment. Of course a fool-prove test also makes the testers feel more safe. But I don’t really think that the above two statements are true:

• Children don’t have to be tested much earlier. They can’t grasp the concept of color yet and don’t need special assistance in daily life until they recognize it themselves.
• Arrangement tests, anomaloscopes and lanterns can’t really be memorized. And even a plates test only needs a shuffle to unmask any potential cheater.

Anyway, the colorblind community is definitely looking forward to get an accurate color vision test which can be used as a standard for many job specific vision tests and as a matter of course a gene therapy to cure color blindness. We will wait patiently for further news…

You can read the whole article from the NMSU here: DNA lab at NMSU partners with company to fight colorblindness. And don’t miss the latest breakthrough in color blindness gene therapy of monkeys.

Yves contacted and told me about this error. What happened? I forgot to perform the chromatic adaptation from D50 to D65 for the sRGB color space. This means I actually assume the XYZ values were taken under a white-blueish D65 light while in reality they were measured under D50 which is white-yellowish. This means I have overestimated the red and underestimated the blue.

Today I updated the test with the new values. The used colors should now be correct and ready to try out: Online D-15 Color Arrangement Test.

I you’ve taken the test previously the result won’t change that much as the colors are just slightly shifted in the color space. My results were still very unpromising: Strongly color blind!

Just the other day I took a picture of a rainbow. It was such a beautiful one, but I couldn’t see the color spectrum so I had to ask my son, if it is really a nice one where you can spot the whole color spectrum. The same would happen if I would work as a professional in the film industry: Either I could ask somebody for help or I just would fail. My color blindness is just to strong to deliver good work.

Truelight Color
Vision Test

FilmLight is a leading company in the film industry and provides a simple online color blindness test on their website. This way you can perform a first check if you are ready to work with moving pictures. Can you spot the T? Check out their website to see the whole Truelight color vision test picture.

This color blindness test picture consists of three lines each showing six T’s. Four of them should be visible and you should be able to tell their orientation. You should also be able to guess the fifth correctly and the sixth is just visible under perfect conditions. The three lines of T’s relate to the three different types protan, deutan, and tritan color vision defects. The test is based on the color blindness confusion lines.

You can’t see anything? — No worries. I can only spot two T’s in the last line. Only if I bend my laptop display back and forth I see two more T’s, but not more.

If you did like this kind of test make sure to check out my color blindness tests or have a look at some other color vision tests online available.

D-15 Color Arrangement Test

The D-15 test is a so called arrangement test. This type of color blindness tests are based on a set of colored plates or discs which have to be arranged in the correct order. Colorblind people will have difficulties to arrange the given colors and make mistakes. Based on this mistakes and the resulting confusion vector, the type of your color blindness and as well its severity can be calculated.

D-15 Protan Test Result

This pictures shows my personal test result. The 16 squares, which have to be arranged in the test, are shown in a circle—which would be the correct sequence. The thick line shows the order I’ve chosen and in this case P-15-1-14-2-3-13-12-4-5-11-10-6-7-9-8.

According to the scoring technique of Vingrys and King-Smith this results in a confusion angle of 1.2 degrees and a confusion index of 3.70. Or in other words I am suffering from a strong protan color vision deficiency, which corresponds with the diagnosis of my eye specialist.

What the D-15 color arrangement test can do:

• Differentiate between protan, deutan and tritan color vision deficiencies.
• Calculate an approximate severity of your color blindness.

… and what this color blindness test can not do:

• Detect some weak forms of color vision deficiency.
• Differentiate between dichromacies and anomalous trichromacies.

Go ahead and check out the online D-15 Farnsworth test and learn some more details about your color vision abilities—or maybe disabilities.