Design and use of the Holmgren Wool test

Abstract

The Holmgren Wool test was commissioned by the Swedish railway authority in 1875 and became a standard test for recruits in many national railway systems. Several different versions of the test have been produced and the test is still commercially available. A new test, purchased in 1990, has 49 wool skeins (3 test skeins and 46 comparison skeins) compared with an older test available in our laboratory having 55 skeins (3 test skeins and 52 comparison skeins). The new test has different coloured wools and a different method of examination is introduced which reduces the number of skeins compared with each test sample. We have evaluated the design of both tests by matching the wools with Munsell papers and obtaining the C.I.E. chromaticity co-ordinates, for source C, from published tables. These data have been compared with established isochromatic zones for protan and deutan colour deficiency. The results show that neither test is correctly designed and that neither of these versions of the Holmgren Wool test has potential for identifying red-green colour deficiency. This conclusion is illustrated by results obtained for six colour deficient observers and three normal trichromats.