Examination of Colour Vision by Use of Induced Contrast Colours

The ability to induce contrast colours is evident in normal persons by the tissue paper contrast principle. However, tests of good quality are not easily available. The design of a new series of charts follows two principles: 1) Selection of background hues in accordance with the maximally desaturated regions of the spectrum as seen by the colour defectives. 2) Exact adjustment of the neutral test field (constituted by the chart figures) in order to eliminate any false clue due to brightness contrasts. By introducing chart figures of alternative grey values appropriate tests can be attained for each type of colour vision defect. 37 persons with congenital colour defect and 15 persons with acquired defects were examined. The charts, according to the criteria for selection, proved to be selective in their screening efficiency.