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Alex R Bowers, Concetta F Alberti, Robert B Goldstein, Eli Peli; Do people with hemianopia spontaneously adapt their gaze scanning to differing hazard detection demands?. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3293.
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© ARVO (1962-2015); The Authors (2016-present)
People with complete homonymous hemianopia (HH) receive no visual cues from peripheral vision as to when or how far to scan into the blind hemifield, yet they may be able to use cognitive/voluntary control to guide their blind-side scanning. We investigated whether HH subjects were able to spontaneously (and without instruction) adapt their blind-side scan magnitudes in response to differing scanning demands for detection of pedestrians in a driving simulator when differing cues about pedestrian eccentricities and movement behaviors were available in the seeing hemifield.
Twelve HH subjects without spatial neglect completed two sessions (each 60 minutes) in a driving simulator pressing the horn when they detected a pedestrian. Stationary pedestrians outside the travel lane were presented in one session and approaching pedestrians on a collision course in the other. Equal numbers of pedestrians were presented at the same eccentricities on the left and right. Eye and head movements were tracked. Gaze movements of ≥ 6° were analyzed for pedestrians initially appearing at ≈14° in the blind hemifield (total 312 events across all subjects). After appearing, the stationary pedestrians’ eccentricity increased rapidly from ≈14° to median 31° after 2.5 s requiring increasingly larger scans for detection while the approaching pedestrians’ eccentricity remained constant at ≈14°, requiring a more moderate scan (≈14°) for detection. No instructions were given about how far to scan to the blind side.
Contrary to expectations, median gaze scan magnitudes did not differ in the two conditions (approaching: 14° [IQR 9-15°]; stationary: 13° [IQR 9-20°]; p = 0.43). Only three subjects showed evidence of adapting (increasing) their gaze scan magnitudes in the stationary condition between the start and end of the session (S5: 20° to 46°; S8: 13° to 26°; S9: 11° to 22° ). Subject S5 also showed adaptive behavior in the approaching condition, decreasing gaze scan magnitudes from 27° (larger than needed to detect pedestrians at 14°) to 11°.
Our results suggest the majority of participants (9/12) did not apply voluntary/cognitive control to modify their blind-side gaze scanning in response to the differing scanning demands of the two conditions despite the information about pedestrian eccentricity available in the seeing hemifield.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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