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Webvision: Color Perception Page 15 of 18 diagnosis of acquired diseases and mild congenital deficiencies. The sequence of test administration include screening for colour vision deficiencies with a pseudo -isochromatic plate test such as the Ishihara and F-2 plate. Failure of either of these tests implies proceeding to the panel D-15. A patient who fails the Panel D-15 is said to be a moderate to severe anomalous dichromat, or a dichromat. A patient who then fails the H-16 is a dichromat or very severe anomalous trichromat, whereas a moderate anomalous trichromat will pass the H-16. A subject who passes the D-15, can proceed to the desaturated D-15, that can pick up the mild anomalous trichomats. The very mild anomalous trichromats who may or may not fail pseudoisochromatic plates can be diagnosed with the Nagel anomaloscope. The Farnsworth 100 -Hue is another arrangement test (figure 26). Unlike the tests mentioned above where the colours are specifically chosen to lie close to the confusion lines, the Farnsworth100-Hue is a discrimination test. Pig= 26. Farnsworth 100-IlucA 2. K ipge 3� ngge) Figure 27 shows where the colours of the 100 -Hue lie on the chromaticity diagram. The colours are chosen to have the same Munsell value and chroma. Originally there were 100 hues, but Farnsworth removed 15 to make the series more uniform. Performance on the Farnsworth 100 - Hue is rated by calculating the total error score. .t~i:+r3 gwDeIh.SM Aff r,5 lid 10 r 62 IRD 74, C AXE iP'g4 y a�6 Fiecim 27. Colours of the i00 -flue on the chromaticity diagram. Point C re rp Clients testing conditions using stanlard illuminant C and poinI Wis the equa_1. energy, whito from Haut W. M. JY Ac. aired dyschromatopsias. Sur, Ovhthalmol 1987• }2• f0) f 16f 16 K 1p_e'g imaged. Lantern tests have been used since thel9th century as a means of assessing colour vision especially for occupational reasons. Lantern tests simulate coloured signal lights. They usually present pairs of red, white and green lights because these are the signal colours used at sea and in air navigation, and the subject is required to name the colours. There are a great number of different lantern tests which vary quite widely in the level of difficulty they present. The level of difficulty depends on the size of the stimulus and its intensity (see Cole and Vingrys 1982 for a http://www.webvision.med.utah.edu/KallColor.html 6/18/01