Abstract

SO.05.03

How important are visual field defects when crossing a road junction? Examination of normal-sighted subjects and patients with homonymous visual field defects under virtual reality conditions

Schiefer U.¹, Papageorgiou E.^1,2, Schoenfisch B.³, Hardiess G.⁴, Mallot H. A.^4
1Centre for Ophthalmology, University of Tuebingen, Germany; ²EU-PERACT MEST-CT-2004-504321; ³Department of Medical Biometry, University of Tuebingen, Germany; ⁴Dept. of Zoology, Lab of Cognitive Neuroscience, University of Tuebingen, Germany

Objective: The visual field plays an important role when evaluating driving fitness. The aim of this study was to assess the effect of homonymous visual field defects (HVFDs) when navigating over a road junction if one also takes into account visual exploration using eye and head movements.
Methods: HVFDs (assessed by binocular semi-automated kinetic perimetry within the 90° visual field, stimulus III4e, 3°/s, with correction for individual reaction times) as well as visual exploratory movements (assessed with eye and head tracking) were superimposed on the trajectories of virtual vehicles on a temporal or spatial scale. The following parameters were visualized and analyzed: (i) Presence versus absence of exploratory movements and – in case of verifiable exploration – (ii) Point in time / distance from the intersection, at which exploration was initiated, (iii) Time span / distance of exploration of a potentially collision-relevant vehicle, and (iv) Resulting modification of driving behavior (in terms of speed change) after / due to exploration of collision-relevant vehicles.
Results: Twenty-seven patients (10 female, 17 male, age range 19-71 years) with HVFDs due to vascular brain lesions (time after lesion at least 6 months) were examined. The control group included 16 normal-sighted subjects with a similar age and gender distribution.
For 17 out of the 27 patients with HVFDs performance (i.e. number of accidents) at the crossroads was comparable to that of the normal-sighted cohort. Patients with left-sided HVFDs due to right-sided brain lesions had a worse driving performance than patients with right-sided HVFDs.
Conclusions: The existence and extent of HVFDs per se seem to be inadequate to predict the successful navigation of an intersection under virtual reality conditions.

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