A redesigned Farnsworth dichotomous B20 test

The Farnsworth dichotomous B20 test has been reconstructed using a circle o f Munsell Hues with value 5. 7 hues have chroma 4, and 13 hues have chroma 2. Results were obtained for 46 normal subjects, 36 subjects with red-green colour deficiency, and 1 congenital tritanope. A larger number of deuternn omalous trichromats fail the reconstructed B20 than fail the Farnsworth D15 test. The B20 test gives good protan/deutan classification, when the test is failed and provides significantly more isochromatic colour configuration s for identifying and classifying tritanopia and tritan colour deficiency t han the D15 test. (C) 2000 John Wiley & Sans, Inc.