Performance of red-green color deficient subjects on the Farnsworth Lantern (FALANT)

Abstract

Background: The Farnsworth Lantern (Falant) is an occupational color vision test intended to identify people with significant red-green color deficiency who are unable to name aviation, marine or railway signal lights correctly. The colors shown are white, green and red selected to be within protan and deutan isochromatic zones.

Hypothesis: The Falant grades the severity of color deficiency and identifies subjects with different types of deficiency.

Method: 270 color deficiency subjects (diagnosed with the Neitz anomaloscope) were examined. A subset of 108 subjects also completed the Farnsworth D15 and the Farnsworth-Munsell 100 hue test.

Results: All dichromats and 75% of anomalous trichromats failed the Falant. The mean error score of dichromats was greater than that anomalous trichromats, but errors were made in a similar number of qualitative color naming categories. The range of Falant error scores was continuous with no demarkation between the criteria for pass and fail. It was not possible to identify anomalous trichromats likely to pass the Falant from the size of the anomaloscope matching range or from the results of Farnsworth-Munsell tests.

Conclusions: People with severe red-green color deficiency fail the Falant, but neither the type nor the severity of color deficiency can be determined either from the qualitative results or from the error score.