Farnsworth Lantern

A type of Lantern (often abbreviated as FALANT); though this original model is no longer produced, it is still oft-used – even sought after – and used models can still cost as much as $5,000, when available. Modern versions like the Optec-900 are still often referred to as the FALANT.

The FALANT was adopted by the US Navy in 1954 to screen for red-green colorblindness and emulates recognizing red, green and white signal lights at night. The FALANT is generally easier to pass than Pseudoisochromatic Plates (e.g. Ishihara Test) or Arrangement Tests (e.g. Farnsworth D-15). When this option is available, applicants to an organization that screens for red-green colorblindness (e.g. the US Navy) often opt to take this test. However, the US Air Force discontinued use of the FALANT in 1993 for these reasons. It is still accepted by the United States FAA as a test for the purpose of obtaining a pilot’s license.

The lantern is designed to be viewed in a light room from about 6m away. It shows simultaneously a pair of vertically oriented lights in combinations of either red, green or yellow-white. The test subject is asked to identify the two colors (some of which are identical). The examinee is shown the target for only two seconds, as Colorblind patients can sometimes correctly identify the colors with prolonged exposure. They then have 5 seconds to name the colors. A Neutral Density Filter is placed randomly in front of one of the colors in order to reduce luminance cues to the Colorblind, and a random order of the light pairs eliminates the possibility of memorization of the test sequence.