Diagnosis and genetics of defective colour vision / by H. Kalmus.

  • Kalmus, H. (Hans), 1906-1988.
Date:
[1965]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Diagnosis and genetics of defective colour vision / by H. Kalmus. Source: Wellcome Collection.

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    CHAPTER VII DIAGNOSIS OF TYPE The classification of defective colour vision is based on matching ability (p. 40) and it would seem only logical that the type of any individual's defect should be best determined by matching devices. Of these the most useful ones are the anomaloscopes. Sometimes where the use of these is impracticable—as in very remote places or where children or people unused to any form of instrument are concerned— certain procedures resembling games with colour blocks have proved quite efficient. As in other fields of medicine, diagnosis of a special kind of colour defect implies a deficiency of a more general kind: if anomaloscopy shows a person to be deuteranomalous, he is obviously colour blind. If by anomaloscopy one could easily and unfailingly discover all kinds of colour defectives, these instruments would be the most useful not only for the typing but also for the discovery of colour defectives and one could dispense with preliminary chart screening. However, as we shall see, dichromats— and in particular deuteranopes—accept a multi¬ plicity of green-red mixtures when matching yellow, which they do predominantly by brightness; and as many of them also accept the normal match, these can easily escape discovery when the anomalo¬ scopy is done by an unskilled person. It is therefore safer—and in the end quicker—when exploring a population's colour vision to use confusion charts first and only test those suspect of a colour defect by anomaloscopy. Even then one should reahze that one's methods must be considered as rather crude, considering that one single measurement only is applied to gauge very crudely a specific fault of one of the most complex systems in existence, namely that of the eye, the visual integrative pathways and the cortex. anomaloscopes Colorimetrie devices for the subjective matching of any colour by mixtures (additions) of two or more spectrally pure hghts are the most 41