The Farnsworth Lantern Flashlight is an accurate, inexpensive substitute for the original Farnsworth Lantern. It compares faithfully to Farnsworth Lantern in construction, chromaticity, and performance with color deficient observers. This test uses nine interchangeable filters that recreate the chromaticity of the original Farnsworth Lantern.
The Farnsworth Lantern has been used since Dean Farnsworth first described it in 1946 for the testing the color signal discrimination ability of color anomalous individuals. This test has found longstanding application in the military and the transportation industry to qualify operators of ships vehicles and aircraft that are known to have failed screening tests such as the Ishhara plates. Because many color deficient persons do have reasonably good signal light discrimination Farnsworth Lantern Test often enables the qualification of these individuals. The original test device has long since stopped being manufactured and more modern equivalents are quite expensive for the limited usage they see in a typical optometrists office. This has resulted in prospective patients often traveling long distances for the test.
The Farnsworth Lantern Flashlight requires 3 D cell batteries and includes a xenon bulb.