Optometry and Vision Sciences - Theses

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An investigation of the blue-sensitive mechanisms of human colour vision

Cole, Barry Leighton ( 1971)

The characteristics of the blue-sensitive process of human colour vision have been explored by means of the two-colour increment threshold technique of W. S. Stiles and the measurement of retinal directional sensitivity. The objectives were a) to find points of difference between the three independent blue-sensitive mechanisms π1, π and π3 which might lead to reasonable hypotheses concerning their physiological basis and functional role, and b) to establish whether the unique threshold behaviour of the blue process at the fovea is due to an absence of blue cones as Wald (1967) has concluded. It has been found that the π3 mechanism has similar characteristics to π1; it is absent in tritanopia, exhibits extensive complete spatial summation and has high directional sensitivity. The π2 mechanism appears to be less directionally sensitive. Both π1 and π3 have been demonstrated at the central fixation area of the fovea. On the basis of these results and evidence in the literature a theory of the blue-sensitive mechanisms is proposed.