Temporal integration in amblyopic vision

Amblyopic subjects were tested on different visual tasks which required temporal integration of successively presented stimuli: a figure had to be detected whose components were displayed successively and hidden in spatio-temporal noise. The time interval T over which the figure elements were dispersed was varied and the longest T value still compatible with figure detection was determined. In all subjects these T values were considerably longer for the normal than for the amblyopic eye. A missing square had to be detected in a checker-board of 3 X 3 squares that was presented in two successive frames, each frame containing 4 squares. With the normal eye, identification of the missing square was possible over considerably longer interstimulus intervals (ISIs) than with the amblyopic eye. Changes had to be detected in two patterns of randomly distributed squares that were presented successively with varying ISI whereby one square was added or subtracted in the second pattern. With the normal eye, detection of changes was possible over much longer ISIs than with the amblyopic eye. These experiments show a deficit of the amblyopic visual system to integrate temporally separated stimuli. We conclude that amblyopia is associated with a marked reduction of the duration of visual persistence and suggest that this is due to shortening of normally sustained neuronal responses.