Rapid compensation of visual search strategy in patients with chronic visual field defects.

INTRODUCTION: The aim of this study was to test the effect and specificity of a novel, compensatory eye movement training therapy designed to improve visual search performance in patients with homonymous visual field defects. METHODS: Seven patients with chronic homonymous visual field defects and six healthy control subjects were tested. All subjects completed the single training period (300 trials). Subjects were assessed on three different saccadic tasks (a visual search task, a rapid scanning task and a reading task) which were evaluated at three time points on the same day: two before and one after the training period. The computer-based training consisted of a novel ramp-step search paradigm that required subjects to pursue a stimulus (ramp phase) and then saccade to find its location when it suddenly jumped (step phase). RESULTS: Pre-therapy we confirmed that patients differed from controls on the visual search task. Post-training we demonstrated a clear improvement in terms of reaction time required to complete the visual search. This effect was confined to: (1) the patient group only; (2) targets presented to the blind visual field of the patients only; (3) the visual search task only and not the rapid scanning or reading task. CONCLUSION: These results demonstrate that rapid, compensatory changes can occur in patients with visual field defects that impact on their ability to carry out efficient visual search. We plan to translate this therapy, along with appropriate testing materials, in a free-to-use, internet-based application based on this intervention