Klinische Neurophysiologie 2014; 45 - P6
DOI: 10.1055/s-0034-1371219

Classification of visual exploratory behavior in patients with homonymous hemianopia

S De Beukelaer 1, J Hamel 2, M Bahnemann 1, S Ohl 3, S Kehrer 1, HJ Audebert 4, A Kraft 1, SA Brandt 1
  • 1Klinik für Neurologie, Charité Campus Mitte, Charité Universitätsmedizin, Berlin, Deutschland
  • 2Department of Neurology, University of Rochester Medical Center, Rochster, NY, USA
  • 3Bernstein Center of Computational Neurosciences, Humboldt Universität zu Berlin, Berlin, Deutschland
  • 4Klinik für Neurologie, Charité Campus Benjamin Franklin, Charité Universitätsmedizin, Berlin, Deutschland

Introduction: Patients with homonymous hemianopia (HH) report to handle quite differently their visual field deficit. We have shown that some patients efficiently use exploratory eye movements directed towards the cortical blind field, while others lack compensatory strategies (Hamel et al. 2012). The aim of the present study was to understand and quantify different visual exploratory strategies in a naturalistic and controlled experimental setting.

Methods: 14 patients were examined in a driving-simulator-paradigm. Eye- and head-movements were recorded via a head-mounted eye-tracking camera (EyeSeeCam, München). Patients were instructed to react towards upcoming obstacles via braking or key pressing as soon as they first detect them. For comparison we included 14 control subjects matched for age, gender, handedness and video gaming experience (Hamel et al. 2013).

Results: The distribution pattern of saccades on the screen was analyzed. Based on the criterion of increased saccadic frequency directed towards the cortically blind field, the patient group was divided into compensators (n = 7) and non-compensators (n = 7). The compensators executed significantly larger mean saccadic amplitudes (p < 0.05). This compensatory mechanism correlated with task performance: while all patients detected accurately the obstacles presented in their sighted hemifield, the compensators missed fewer obstacles in their blind hemifield than non-compensators (p < 0.001).

Conclusions: Eye movement patterns reflect different compensatory strategies after HH. Half of the patients had significantly larger saccades and a higher ratio of saccades towards the blind hemifield, resulting in better task performance. Future studies should test if non-compensators can learn compensatory visual exploratory strategies over a series of training sessions.