Integration of local orientation in strabismic amblyopia

In order to investigate the processes which integrate local orientation information in observers with strabismic amblyopia, we measured contrast thresholds for discriminating the global orientation of a pattern (3 "bars") comprised of Gabor patches. We found that in both eyes of amblyopic observers, as has been reported for normal observers [Saarinen, Levi & Shen (1997) Proceedings of the National Academy of Sciences USA, 94, 8267-8271], there is an approximately two-fold enhancement of contrast sensitivity when the global and local orientations are aligned (relative to mixed orientations), and a smaller enhancement when the global and local orientations are orthogonal. This orientation dependent enhancement occurs despite substantial losses of contrast sensitivity. These results suggest that the integration processes in the amblyopic eye that operate to enhance detection are essentially intact.