The site and nature of suppression in squint amblyopia.

A significant percentage of humans have a misaligned eye (squint) due to a disruption of early visual development. In later adult life these people do not experience double vision because the visual information from their misaligned eye is actively suppressed within their visual system. Here I utilize a phenomenon called spatial adaptation which is known to have its site in the striate cortex to answer the question "is the site of suppression before, at, or after the site of adaptation?" Strabismic amblyopes who display spatial adaptation when viewing monocularly with their amblyopic eye fail to display adaptation through their amblyopic eyes under binocular viewing conditions. The lack of adaptation depends on the orientational difference between the adapting stimuli seen by each eye under binocular viewing conditions. These results suggest that suppression occurs at rather than before or after the first site of adaptation.