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


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          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.


          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.


          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.


          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.

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          Most cited references19

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          Line bisection and unilateral visual neglect in patients with neurologic impairment.

          Unilateral visual neglect is a common symptom or sign in patients with lesions of the nondominant hemisphere. Several techniques have been used to demonstrate visual neglect. One such technique--asking a patient to bisect a horizontal line and expecting an estimate of center away from the side neglected--has been used for over 70 years but has not been statistically evaluated. We conducted a formal evaluation of this method and found that under special conditions, line-bisection performance can discriminate between patients with right-hemisphere lesions and patients with diffuse lesions, patients with left-hemisphere lesions, and hospital controls. When used to investigate visual neglect in an individual patient, the line-bisection test should be given in conjunction with other complementary procedures such as symmetric drawings and the Memory-for-Designs Test.
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            Driving with hemianopia, I: Detection performance in a driving simulator.

            This study was designed to examine the effect of homonymous hemianopia (HH) on detection of pedestrian figures in multiple realistic and hazardous situations within the controlled environment of a driving simulator. Twelve people with complete HH and without visual neglect or cognitive decline and 12 matched (age, sex, and years of driving experience) normally sighted (NV) drivers participated. They drove predetermined city and rural highway routes (total, 120 minutes) during which pedestrian figures appeared at random intervals along the roadway (R-Peds; n = 144) and at intersections (I-Peds; n = 10). Detection rates and response times were derived from participant horn presses. Drivers with HH exhibited significantly (P < 0.001) lower R-Ped detection rates on the blind side than did NV drivers (range, 6%-100%). Detection of I-Peds on the blind side was also poor (8%-55%). Age and blind-side detection rates correlated negatively (Spearman r = -0.71, P = 0.009). Although blind-side response times of drivers with HH were significantly (P < 0.001) longer than those of NV drivers, most were within a commonly used 2.5-second guideline. Most participants with HH had blind-side detection rates that seem incompatible with safe driving; however, the relationship of our simulator detection performance measures to on-road performance has yet to be established. In determining fitness to drive for people with HH, the results underscore the importance of individualized assessments including evaluations of blind-side hazard detection.
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              Most naturally occurring human saccades have magnitudes of 15 degrees or less.


                Author and article information

                Transl Vis Sci Technol
                Transl Vis Sci Technol
                Translational Vision Science & Technology
                The Association for Research in Vision and Ophthalmology
                September 2017
                23 October 2017
                : 6
                : 5
                : 11
                [1 ]Department of Psychology, College of Science, Northeastern University, Boston, MA, USA
                [2 ]Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, USA
                Author notes
                Correspondence: Alex Bowers, Schepens Eye Research Institute, 20 Staniford Street, Boston MA 02114, USA. e-mail: alex_bowers@ 123456meei.harvard.edu
                tvst-06-05-12 TVST-17-0502
                Copyright 2017 The Authors

                This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

                : 24 March 2017
                : 06 September 2017

                head movements,eye movements,gaze,detection,adaptation,hemianopia,rehabilitation


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