Alternating exotropia: temporal course of the switch in suppression

The exotrope usually suppresses the input from the temporal retina of the deviating eye. Some exotropes can alternate the eye which is used to fixate. When this happens, the suppressing and fixating eyes trade roles in what appears to be less than 80 msec (about the time it takes to make a large saccade). The temporal course of this switch in fixating/suppressing eyes was measured by flashing patterned stimuli to the exotrope before, during, and after the eye movement used in making the switch. Polaroid lenses were used to dissociate the visual input to the two eyes, and binocular eye movements were recorded with a photoelectric technique. It was found in three alternators that the switch in suppression begins as soon as the eyes start to move and is completed before the end of the saccade used to make the switch.