Colour conveys useful information about the spectral composition of the light and the reflectance properties of objects. It is only one of many attributes of vision that enable us to process and interpret complex information in the visual world, effortlessly and almost instantaneously.
Colour signals yield significant advantages in many visual tasks and in some occupations, the normal processing and correct interpretation of colour signals is also safety-critical. Subjects with congenital colour deficiency and those with diseases of the eye or systemic diseases such as diabetes exhibit either anomalous or even complete absence of red/green and / or yellow/blue colour vision. The accurate assessment of colour vision is therefore important, both in occupations as well as in the clinic, when high sensitivity and specificity are essential requirements.
The visual system makes use of several signals to construct the best representation of the visual world, based on the spatiotemporal and chromatic properties of the retinal image. The complex algorithms involved produce a faithful representation of the visual world with rare exceptions, when ambiguities result in visual illusions.
Because of the multiple signals involved in the representation of any coloured object, conventional colour assessment tests fail to isolate uniquely either red/green or yellow/blue colour signals, and also do not eliminate all the cues an applicant can use to carry out the task. Detailed analysis of current colour assessment protocols used in visually demanding and safety critical occupations reveals large variability, compromised safety and highlights the often inconsistent and unjust outcomes.
A new approach to colour assessment that overcomes these problems will be described. In addition, experiments designed to reveal the limits of red/green and yellow/blue colour discrimination one can achieve in human vision will be presented.