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.

    51/134 (page 35)
    THE DETECTION OF DEBECTIVE COLOUR VISION 37 Various standard illuminants have been defined firom time to time and a few^ models will be mentioned below: Ordinary tungsten light enables many deutans to read many pseudo-isochromatic charts correctly; it is less misleading for protans. Similarly most artificial Hghts will invalidate wool tests, Famsworth tests and all others depending on pigments and reflected light. An iUuminant-stable colour vision test consisting of six charts which may be read in daylight or incandescent light has been devised by Ellis Freeman (1948). But its efficiency in other respects has not been fully tested. Viewing distance also affects chart readings as colour matching depends on field size (Homer and Purslow, 1947-48; Jaeger and Kroker, 1952). The effects of very small fields producing tritanopic vision are described on p. 21. Therefore, charts should be used at ordinary reading distance or at the distance stated; refraction errors should be corrected by wearing glasses, but these must not be tinted. NageVs Charts (Bergmann, Wiesbaden, Germany) The working of these charts depends on colour naming. First published in 1898, each of the charts carries a circle of 23 coloured dots of various hues, some of them being more or less red. In a prehminary run the subject is shovm aU the charts and asked whether each contains a red dot. People not making any mistakes are judged to be normal, but a single mistake makes a person suspect of defective colour vision and he is then retested and asked additional questions according to instructions. The charts are not suited for mass screening, but allow some subclassification. Stilling's Charts (20th edition by Hertel, Leipzig) These, the first widely used colour charts (1878), are still used on the continent of Europe and in Latin America. It has been stated that they are less efficient in discovering and classifying colour defectives than more modern charts. On the other hand, unlike the other col-