A test for colour blindness in which the patient matches coloured skeins of yarn. The test is based on the Young-Helmholtz theory of colour perception which states that there are three sets of colour perceiving elements in the retina. According to the theory, a defect in one of these elements causes a variant of colour-blindness.
See also Young-Helmholtz three colour theory, under Thomas Young, English physician and physicist, 1773-1929.
- George Wilson (1818-1859):
Researches on colour-blindness. With a supplement on the danger attending the present system of railway and marine coloured signals.
Edinburgh: Sutherland & Knox; London: Simpkin, Marshall and Co., 1855.
The first book on colour-blindness, and the most important monograph on the subject until the publication of Holmgren's work in 1877. It first began to appear in the November 1853 issue of the Edinburgh Monthly Journal of Medical Science, and was continued in the Transactions of the Royal Scottish Society of the Arts, before being published in book form. Wilson was the first in Britain publicly to point out the potential hazards of colour-blindness in railwaymen and seamen.
- A. F. Holmgren:
Om färgblindheten i dess förhållande till jernvägstrafiken och sjöväsendet.
Upsala Läkareförenings Förhandlingar, 1876-1877, 12: 171-251, 267-358.
German translation: Die Farbenblinheit in ihren Beziehungen zu den Eisenbahnen und der Marine. Leipzig, 1878.
English translation in: Annual Report of the Smithsonian Institution for the year 1877. Washington, 1878: 131-200. Om färgblindhet och den Young-Helmholtz’ske färgteorien.
Upsala Läkareförenings Förhandlingar.