Contour integration in strabismic amblyopia: the sufficiency of an explanation based on positional uncertainty

Contour integration was measured in a group of strabismic amblyopes to determine if an explanation based solely on positional uncertainty was sufficient to explain performance. The task involved the detection of paths composed of micropatterns with correlated carrier orientations embedded in a field of similar micropatterns of random position and orientation (Field et al. Contour integration by the human visual system; Evidence for a local "association field". Vision Research, 33, 173-193, 1993). The intrinsic positional uncertainty for each amblyopic eye was measured with the same stimulus and it was found that in 10 out of our 11 amblyopic subjects, the reduced performance of the amblyopic eye could be modelled by the normal eye with an equivalent amount of positional uncertainty added to the stimulus. We conclude that the rules by which cellular outputs are combined, at least as reflected by this task, are normal in amblyopia.