Chromatic sensitivity and tinted lenses: A preliminary study with the CAD test

The aim of this study was to assess the extreme effects of tinted lenses on colour vision by examining changes in chromatic sensitivity when viewing visual displays through a slightly tinted ("blue-blocking") filter and through a heavily tinted, "orange" coloured filter. The CAD test was used to measure both red/green (RG) and yellow/blue (YB) chromatic sensitivity in ten subjects when viewing visual displays through each of the two filters. The measured RG and YB colour thresholds were then compared with similar measurements made without coloured filters in front of the eye. The blue-blocking filter absorbs only a small amount of short- wavelength light, whilst the "orange" filter preferentially attenuates more short- wavelength and some middle-wavelength light. The results show that the blue- blocking filter does not significantly affect either RG or YB colour vision. The orange filter, on the other hand, causes large changes in colour discrimination. The results were statistically analysed by comparing the results obtained with the coloured filters with those measured without any filters in front of the eye. More experimental work is now needed to establish how much short-wavelength light can be removed without significantly affecting the subject's colour discrimination performance.