The Farnsworth Lantern Test, or FALANT, is a

color vision test A color vision test is used for measuring color vision against a standard. These tests are most often used to diagnose color vision deficiencies (''color blindness''), though several of the standards are designed to categorize normal color vision ...

originally developed specifically to screen sailors for tasks requiring

color vision Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different wavelengths (i.e., different spectral power distributions) independently of light intensity. Color perception is a part of ...

, such as identifying signal lights at night. It screens for red-green deficiencies, but not the much rarer blue color deficiency.

History

The test was developed by Dr.

Dean Farnsworth Dean may refer to: People * Dean (given name) * Dean (surname), a surname of Anglo-Saxon English origin * Dean (South Korean singer), a stage name for singer Kwon Hyuk * Dean Delannoit, a Belgian singer most known by the mononym Dean Titles * ...

(Commander, United States Navy) while stationed at the Naval Submarine Research Laboratory in

New London, Connecticut New London is a seaport city and a port of entry on the northeast coast of the United States, located at the mouth of the Thames River in New London County, Connecticut. It was one of the world's three busiest whaling ports for several decades ...

during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

. After its adoption by the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

in 1954 as the standard color vision test for sailors aboard ship, it has additionally been used to screen flying personnel.

Test Procedure

The test consists of showing a pair of vertically oriented lights consisting of combinations of either red, green or yellow-white. The test subject is asked to identify the two colors (some of which are identical). Nine color pairs are administered during the test, beginning with a red/green combination, to allow the patient to see these two colors prior to seeing a white light, which decreases testing errors. The examinee is shown the target for only two seconds, as color-deficient patients can sometimes correctly identify the colors with prolonged exposure. The yellow-white light, or one of the identical paired lights, employs a 50% neutral gray filter to reduce luminance cues to the color-deficient patient. Random presentation reduces memorization of the test sequence by motivated persons.

Results Assessment

Errors by color-deficient patients tend to be of two types. The first is mis-calling the white light the complement of the colors presented. For example, red-white is said to be "red-green", or green-white is called "green-red". The second is when a pair of lights of the same color but differing in brightness by 50% is displayed, the brighter identical color is said to be "white". For example, green(dim)-green(bright) is called "green-white". Dichromats, by definition, cannot distinguish any of the colors, and only make correct answers by random guessing. The Military Medical Purchase Description specifies the lights in the FALANT in terms of percent luminous transmittance and 1931 CIE x,y chromaticity coordinates, calculated from Illuminant A, from spectrophotometric measurements of the glass filter components that make up the lantern. Illuminant A is approximated by a 115 volt, 40 watt T8 tungsten lamp inside the FALANT. By design, the FALANT allows mild color-blindness conditions to pass the test, while still excluding most of the moderate or severe cases of color-deficiency. The test is intended to mimic the types of situations requiring color vision that a sailor would find while serving aboard a ship. A passing test is no mistakes in the first nine pairs, or only two mistakes in the eighteen presentations shown to the examinee.

Test Evaluation

Research has shown a sensitivity of only 25% for detecting color vision deficiencies, and occasionally the FALANT allows moderate or even severely color deficient trichromats to pass, especially if given enough attempts with allowed errors, or given improperly by the technician. Administration errors are frequent, when not given in the correct lighting conditions, timing or distance. Testing errors are reduced by standardization of the verbal instructions, rules for administration, and scoring method. Four important phrases are: (1) "Remember, only three colors - red, green, and white", (2) "They look like signal lights at a distance", (3) "Call out the colors as soon as you see them", (4) "They can be in any combination or the same".

Usage in Aviation

The FALANT is accepted by the

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Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...

as a test of color vision for the purpose of obtaining a pilot's license. However, the

United States Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...

discontinued use of the FALANT in 1993 due to its frequent failure to identify cases of color blindness considerably more serious than the test was intended to let pass. The original FALANT apparatus is no longer manufactured, but many modern equivalents of various levels of sophistication are available today, such as the Optec-900.

References

External Links

Colorlite browser simulation of FALANT
{{Color topics Color vision Diagnostic ophthalmology Aviation safety Eye procedures Test items