Monocular eye patching modulates ipsilesional reactive saccades and smooth pursuit in patients with left hemispatial neglect

Patients with hemispatial neglect show multiple oculomotor deficits like delayed contralesional saccade latencies, hypometric saccade amplitudes, and impaired smooth pursuit. We aimed to investigate whether modulation of superior colliculus (SC) activity via monocular eye patching improves neglect patients’ eye movements to the contralesional side of space. Thirteen neglect patients with left-hemispheric (LH) stroke, 22 neglect patients with right-hemispheric (RH) stroke, and 24 healthy controls completed a video-oculographic examination of horizontal smooth pursuit and reactive saccades twice, while the left or right eye was covered with an eye patch. Independent of the eye patch position, LH and RH patients showed enlarged saccade latencies toward contralesional stimuli. In addition, both during smooth pursuit and reactive saccades, RH patients made significantly fewer rightward saccades when the right than when the left eye was patched. Moreover, during reactive saccades, RH patients made significantly fewer right than left saccades, but only when the right eye was patched. These findings suggest that the ipsilesional eye patch modulated ipsilesional ocular performance in the RH group, presumably resulting from differences in SC activity. Yet, ipsilesional eye patching did not improve eye movements to the contralesional side of space, possibly due to the incomplete contralateral retinocollicular projection in humans.