The dissatisfaction expressed by those who are required to undergo examinations for color vision is general and in railway service it even extends to the officials. This has created a demand for some test supplementary to the Holmgren wool test which is universally used.
The fact that, in practice, railway men and pilots are dependent at night on light transmitted through colored glass has caused an endeavor to devise a test which shall, as nearly as possible, approximate the actual conditions; hence the lanterns. Many are in general use on a number of our largest railway systems. Dr. Charles H. Williams' lantern is probably the best in this country (Fig. 1).
It is conceded that the worsted test of Holmgren will not detect all kinds of color defects, but it must be also granted that no other known test will, and that the Holmgren test is equal, if not superior,
BLACK NM. A NEW SUPPLEMENTARY TEST FOR COLOR VISION. JAMA. 1906;XLVI(25):1902–1906. doi:10.1001/jama.1906.62510520006002a
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