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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    the detection of defective colour vision 35 1 II III IV V VI © Fig. 13. Patterns of Maxwell's spot as it appears to normal observers. nations, pseudo-isochromatic charts are the most frequently used screening device for the detection of defective colour vision. These confusion charts (Wright, 1957) are based on the existence of iso-colour zones (pp. 8-10) and consist of patterns of variously coloured dots, containing some number, letter or other shape w^hich the subject is asked to read, or if illiterate or a child, to trace; most of the charts of any series are read by colour normals but not by colour defectives or by certain classes of them. In several series of these charts some are contained which colour defectives read more easily or read differently from normals. The relative merits of the various collections of these charts—some of which will be described later—^have been compared, but such evaluations are imfortunately not too useful because successive editions of the same charts have been shown to differ in their colours. Great caution is required in the special interpretation of readings. Thus the German style of the numbers in Stilling's tables differs somewhat from the English shapes; Spanish-speaking people make systematic mistakes when reading the Ishihara tables. More seriously, Arab people use numerals which are entirely different from the I : halo, clearing, central spot II : halo, narrow clearing, central spot III : halo, cut-up clearing, central spot IV : halo, no clearing, central spot V : homogeneous disc VI : halo, clearing, no central spot (from Izobe, 1955).