Driving with Hemianopia V: Do Individuals with Hemianopia Spontaneously Adapt Their Gaze Scanning to Differing Hazard Detection Demands?

PURPOSE We investigated whether people with homonymous hemianopia (HH) were able to spontaneously (without training or instructions) adapt their blind-side scan magnitudes in response to differing scanning requirements for detection of pedestrians in a driving simulator when differing cues about pedestrian eccentricities and movement behaviors were available in the seeing hemifield. METHODS Twelve HH participants completed two sessions in a driving simulator pressing the horn when they detected a pedestrian. Stationary pedestrians outside the driving lane were presented in one session and approaching pedestrians on a collision course in the other. Gaze data were analyzed for pedestrians initially appearing at approximately 14° in the blind hemifield. No instructions were given regarding scanning. RESULTS After appearing, the stationary pedestrians' eccentricity increased rapidly to a median of 31° after 2.5 seconds, requiring increasingly larger blind-side gaze scans for detection, while the approaching pedestrians' eccentricity remained constant at approximately 14°, requiring a more moderate scan (∼14°) for detection. Although median scan magnitudes did not differ between the two conditions (approaching: 14° [IQR 9°-15°]; stationary: 13° [IQR 9°-20°]; P = 0.43), three participants showed evidence of adapting (increasing) their blind-side scan magnitudes in the stationary condition. CONCLUSIONS Three participants (25%) appeared to be able to apply voluntary cognitive control to modify their blind-side gaze scanning in response to the differing scanning requirements of the two conditions without explicit training. TRANSLATIONAL RELEVANCE Our results suggest that only a minority of people with hemianopia are likely to be able to spontaneously adapt their blind-side scanning in response to rapidly changing and unpredictable situations in on-road driving.