Troxler’s effect at low scotopic luminances. Dependence on target shape and orientation.

Year: 1972

Authors: Ronchi L., Molesini G., Viliani G.

Autors Affiliation: Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, Italy

Abstract: The total disappearance time under steady fixation, in peripheral vision, for the dark-adapted retina, is found to differ when passing from an annulus to a line-shaped target. In addition, it is found to depend on the orientation of the line. This effect takes place at luminances so close to absolute threshold, that no appreciable after-image is perceived. Now, Troxler’s effect shows one preferred orientation, while there is a paramount of evidence, in the visual literature, in favour of the existence of two preferred orientations. It is suggested that the two preferred orientations mirror the neural organization at two different levels, in the neural pathway, and that Troxler’s effect involves only one of these levels, say, the most peripheral one.


Volume: 27(4)      Pages from: 547  to: 557

KeyWords: eye; visual perception; physiological optics