Lantern test (Beyne)

Tritest L3 (Luneau France)

The Lanterntest to Beyne is a test method for studying the color vision of the respective subject. The test persons are mostly people who already have a color vision disorder or who have been diagnosed with an alleged color vision disorder using the Ishihara color table. With such people, the question arises as to whether they can exercise certain professions (for example the profession of pilot ). In addition to France and the United Kingdom , this test procedure is also recognized in Germany , where it is carried out at the German Aerospace Center (DLR) in Cologne . The idea behind the test is to create a situation that is as realistic as possible by showing the test person individual small points of light in the colors red, green, blue, white and yellow in random order and for brief moments in a darkened room. The test person must be able to name these without errors.

Approximate floor plan of the room in which the lantern test is carried out at DLR in Cologne

history

The process was invented by the French military doctor Jules Beyne (1880–1968), who held a leading position in the development of French aviation medicine in the 1930s. Many devices were distributed to French military hospitals, among others. There were several versions of the device. The test device is no longer in production.

Until the end of the 2000s, the test person was shown and named each color beforehand. The test was then carried out with ten presentations. The lantern test in Cologne was carried out with the following parameters until August 2018. So far, the test has been repeated immediately afterwards if the test person only made one mistake.

parameter
property	value
Distance test subject / test device	${\ displaystyle 5 \, \ mathrm {m}}$
Size ( ) of the point of light ${\ displaystyle d}$	${\ displaystyle 3 '= {\ frac {3} {60}} ^ {\ circ}}$ That means in this case: ${\ displaystyle d = \ tan \ left ({\ frac {3} {60 \ cdot 2}} ^ {\ circ} \ right) \ cdot 5 \, \ mathrm {m} \ cdot 2 \ approx 4 {,} 363323 \, \ mathrm {mm}}$
Display duration	${\ displaystyle 0 {,} 5 \, \ mathrm {s}}$
Time for reply	${\ displaystyle 3 \, \ mathrm {s}}$ after the lights go out
Number of ads	${\ displaystyle 12}$ (plus one white at the beginning) or in exceptional cases (plus one white at the beginning) ${\ displaystyle 24}$
Number of repetitions per color	Red: Green: Blue: White: Yellow: or in exceptional cases twice as many ${\ displaystyle 3}$ ${\ displaystyle 3}$ ${\ displaystyle 2}$ ${\ displaystyle 3}$ ${\ displaystyle 1}$
Number of light points per display	1

Implementation (Germany)

A test leader stands next to the device and an assistant sits behind the test person. The task of the test leader at the device is to operate the device as well as to explain the procedure before the test. The task of the assistant behind the test person is to write down the test person's answers. Before the test begins, the test leader explains the test by reading a pre-defined text to the test person, which reads:

The purpose of this test is to determine whether you are able to reliably differentiate and name the colors red, green, blue, white and yellow. The colors light up for about one second and then you have three seconds to respond. A wrong answer cannot be corrected and hesitation is also counted as a mistake. An error-free test is considered passed. Before the test, we give your eyes three minutes to adjust to the darkness. Then we will show you the color white as the first light. The white is a very dirty or yellowish white and the yellow is referred to as orange by some people. You can also call the yellow orange or yellow-orange, but you should always call the white white. Before every next color I prepare you for it with the words “The next one”. If you don't have any more questions, I'll turn off the light. After three minutes I'll show you the color white.

The test leader then switches off the light and sets an egg timer to three minutes. The room is absolutely dark so that the test person cannot see anything. As soon as the egg timer rings, the test leader sets the test person to the coming white, which is then shown for half a second. The test then begins with the following parameters:

parameter
property	value
Distance test subject / test device	${\ displaystyle 5 \, \ mathrm {m}}$
Size ( ) of the point of light ${\ displaystyle d}$	${\ displaystyle 3 '= {\ frac {3} {60}} ^ {\ circ}}$ That means in this case: ${\ displaystyle d = \ tan \ left ({\ frac {3} {60 \ cdot 2}} ^ {\ circ} \ right) \ cdot 5 \, \ mathrm {m} \ cdot 2 \ approx 4 {,} 363323 \, \ mathrm {mm}}$
Display duration	${\ displaystyle 0 {,} 5 \, \ mathrm {s}}$
Time for reply	${\ displaystyle 3 \, \ mathrm {s}}$ after the lights go out
Number of ads	${\ displaystyle 24}$
Number of repetitions per color	Red: Green: Blue: White: Yellow: ${\ displaystyle 6}$ ${\ displaystyle 6}$ ${\ displaystyle 4}$ ${\ displaystyle 6}$ ${\ displaystyle 2}$
Number of light points per display	${\ displaystyle 1}$

Example of a lantern test according to Beyne (colors: see description)

The test person will be informed shortly beforehand of the next ad with the words “The next one”. Between presentations, the test supervisor uses a flashlight to see his own documents. Although the test person notices this, it is usually not perceived as annoying by them. He / she answers after each advertisement with “red”, “green”, “blue”, “white” or “yellow” / “yellow-orange” / “orange” or says nothing if he / she chooses the color of the point of light shown can not name. If he / she did not make a mistake, the test is considered passed. If he / she has made one or more mistakes, it is considered failed. At the end he / she receives a forgery-proof ( stamp of the DLR, forgery-proof paper) to be presented to the aviation doctor, on which the test result (color-safe / not color-safe) is ticked by machine and the name of the test person is written. If the test fails, the reason is not given, i.e. the test person does not know which colors they named incorrectly. In addition, a fee of 125 euros (as of 2018) will be charged in advance for carrying out the test. If the test is not passed, the test can be repeated every six months, but the acquisition of the Medical 1 is initially denied in Germany . There is a VCL notice on the Medical 2 , which prohibits flying at night. Nevertheless, every flight license can be acquired from a glider pilot license (SPL) to a private pilot license (PPL) - with restrictions under certain circumstances. The Lanterntest to Beyne the medicals can be carried out in Germany, either on its own initiative or on referral to the LBA by the competent flight surgeon after failing. The second case is referred to in EASA terminology as the "secondary review procedure" (English for second or special reports). According to EASA regulations, every pilot candidate who is denied his medical training has a right to this special report.

The test device

Tritest L3 Luneau France (from four perspectives)

The device is made by the manufacturer Luneau France with the name Tritest L3 . Another name for the device or the test procedure is Beyne Type 2 (Aviation) . The device is no longer produced. The production period of the test device at DLR is around the 1980s. The first devices of this kind were produced by another manufacturer as early as 1951 and are known as the "original Beyne Lantern".

In front of the device is a cylinder with a black peephole on the side through which the test leader can see the color of the current presentation. In addition, there is a setting wheel on the other side of the cylinder that the test leader can use to set the color of the presentation (white, green, red, blue, yellow-orange and some double colors). There are two lenses on the front of the device: the Compur shutter, with which it is possible to set exact exposure times and light point sizes, and a lens that is permanently translucent and offers no adjustment options. In contrast to the Compur shutter, however, it offers the option of displaying two points of light one above the other. Depending on requirements, the respective lens must be screwed onto the actual light output in the middle of the cylinder on the front of the device.

The device used at DLR in Cologne has the following properties:

The electricity is drawn from a normal Euro socket

A light bulb serves as the light source

The display time is variable (1/500 second to 1 second with Compur shutter, permanent display with lens)

The size of the light point is variable (1 'to 6', see angular minute for Compur shutter, open for lens)

It can be set whether the test person is shown one or two light points at the same time (two light points can only be displayed when the lens is screwed on)

A product of the Compur type with size # 0 is used as the closure

Shortly after the test leader has triggered, the device makes the sound of a spring mechanism (typical for the timing of a Compur shutter ). The test parameters at DLR in Cologne always remain the same (see table above).

The colors

Illustration of the colors of the Beyne Lantern with the different opening angles

As mentioned earlier, the colors red, green, blue, white and yellow are shown. Studies have shown that even people with normal vision have difficulties with the colors white and yellow. The white corresponds to the color of an incandescent lamp and can therefore be described as dirty white, warm white (approx. 2450 K) or light beige / sand colors . Some also refer to the color as yellow, but this does not match the official name for this color. The yellow corresponds to the color of a car indicator or a warning light and is sometimes also referred to as yellow-orange or orange. The colors red, green and blue also refer to those with normal sight as these colors. There are therefore no special features with them.

Wavelengths, luminances and CIE coordinates of the colors
colour	wavelength	Luminance	CIE coordinates (1931)
red	623 nm	unknown	${\ displaystyle (0.700,0.300)}$
green	530 nm	unknown	${\ displaystyle (0.200,0.700)}$
blue	465 nm	${\ displaystyle 5 \, \ mathrm {\ frac {cd} {m ^ {2}}}}$	${\ displaystyle (0.140,0.070)}$
White	583 nm	unknown	${\ displaystyle (0.495,0.440)}$
yellow	595 nm	${\ displaystyle 85 \, \ mathrm {\ frac {cd} {m ^ {2}}}}$	${\ displaystyle (0.600,0.400)}$

Effect on people with color vision impairment

Both people with a deuteranomaly and with a protanomaly have difficulties distinguishing green and white from one another, depending on their severity. In the case of the protanomaly , problems often arise in distinguishing between red and yellow-orange. In the study by City University in London, only people with normal vision and test persons with a deuteranomaly had a chance of passing. For people with deuteranopia (green blindness), protanopia (red blindness) or monochromaticity (color blindness in the true sense of the word ) there is almost no possibility of passing the lantern test according to Beyne , since they cannot distinguish the affected light from another affected light based on its color can distinguish. If a person does not recognize the color of a light due to their color vision impairment, they may still be able to recognize it based on its brightness and / or saturation. By stipulating that the test may only be repeated every six months and that the test person may not be told the reason for the test result, this “learning effect” is counteracted, among other things. It is not possible to remember the exact saturation or brightness of a color over six months. In addition, you cannot assign this if the actual test result is concealed from you.

Legal basis

The EASA regulation of 2011 states the following for dealing with people with color ametropia with regard to their medical fitness as an aircraft pilot:

"AMC1 MED B.075 Color vision

(a) At revalidation, color vision should be tested on clinical indication.

(b) The Ishihara test (24 plate version) is considered passed if the first 15 plates, presented in a random order, are identified without error.

(c) Those failing the Ishihara test should be examined either by:

(1) anomaloscopy (Nagel or equivalent). This test is considered passed if the color match is trichromatic and the matching range is 4 scale units or less; or by

(2) lantern testing with a Spectrolux, Beynes or Holmes-Wright lantern. This test is considered passed if the applicant passes without error a test with accepted lanterns. "

Translation:

"AMC1 MED B.075 color vision

(a) If the medical is extended, color vision must be clinically tested.

(b) The Ishihara test (version with 24 test images) is passed if all 15 test images, presented in random order, are recognized without errors.

(c) Individuals who fail the Ishihara test must be examined as follows:

(1) Anomaloscope (nail or similar). This test is passed if the color comparison is trichromatic and the setting range is 4 scale units or less, or

(2) Lantern test with a Spectrolux, Beynes or Holmes-Wright Lantern. This test is passed if the test person passes one of the accepted tests without fail. "

Although three different types of this Directive Lanterntests are specified, only coming Lanterntest to Beyne applied in Germany.

criticism

The Beyne lantern test has already come under international criticism several times and has been examined in several studies in which the results of normally sighted test persons were compared with those of test persons with a color vision disorder . Moreover, the results of were Lantertests to Beyne with the results of other Lanterntests ( Farnsworth , Spectrolux etc.) were compared. It turned out that around 50% of the subjects without color vision impairment failed the test in at least one run. In addition, the results were not always reproducible, so it happened that a test person achieved different results in several runs. The study shows: in principle, even if one or two failed lantern tests, it can be assumed that the next test will be passed.

This study was done by considering a series of five colors (red, green, blue, white, and yellow in random order) as one run. Since from now on twenty-four (instead of five) colors are shown, the probability of passing this test decreases even for people with normal vision. Although the test person is told that they will see the colors for a second, they are only presented for half a second. This fact, together with the large number of presentations, makes a huge difference.

In addition, the same standards do not apply everywhere in the world as in Europe and thus in Germany. Therefore, foreign pilots who might never have received a license in Germany due to their color ametropia are still allowed to fly through German airspace . In the United States , for example , a completely different test method, the so-called Medical Flight Test (MFT), is standard. The test persons must be able to recognize and name details in the landscape, colors of lights in and outside the cockpit and other things under real conditions (a flight is carried out). This test is much easier for the test person to pass and also much closer to reality.

literature

Theresa J. Squire, Marisa Rodriguez-Carmona, Anthony DB Evans, and John L. Barbur: Color Vision Tests for Aviation: Comparison of the Anomaloscope and Three Lantern Types from Aviation, Space, and Environmental Medicine Volume 76, No. 5, May 2005

Civil Aviation Authority: Minimum Color Vision Requirements for Professional Flight Crew - Part 1 (August 14, 2006) ISBN 0-11-790622-0

European Aviation Safety Agency: Acceptable Means of Compliance and Guidance Material to Part-MED (December 15, 2011)

Joint Aviation Authorities: JAA Manual of Civil Aviation Medicine (June 1, 2009) -> see "Beyne's protocol"

Patrick Hermsmeyer: Report: Color vision impairment and fitness to fly (November 1, 2018)