The Effect of Visual Field Defects on Driving Performance

Abstract

To investigate the effect of visual field defects on driving performance, and to predict practical fitness to drive. Methods: The driving performance of 87 subjects with visual field defects due to ocular abnormalities was assessed on a driving simulator and during an on-road driving test. Outcome Measures: The final score on the on-road driving test and simulator indexes, such as driving speed, viewing behavior, lateral position, time-headway, and time to collision. Results: Subjects with visual field defects showed differential performance on measures of driving speed, steering stability, lateral position, time to collision, and time-headway. Effective compensation consisted of reduced driving speed in cases of central visual field defects and increased scanning in cases of peripheral visual field defects. The sensitivity and specificity of models based on vision, visual attention, and compensatory viewing efficiency were increased when the distance at which the subject started to scan was taken into account. Conclusions: Subjects with visual field defects demonstrated differential performance on several driving simulator indexes. Driving examiners considered reduced speed and increased scanning to be valid compensation for central and peripheral visual field defects, respectively. Predicting practical fitness to drive was improved by taking driving simulator indexes into account.

Assessing Driving Performance with Moderate Visual Field Loss

“…By comparison, in an on-road study of drivers with more restricted peripheral fields than the range in this study (mean 84° ± 35°compared to 123° ± 20° here), only 43% passed a test of practical fitness to drive (Coeckelbergh et al, 2002). As previously reported for drivers with a diagnosis of glaucoma (McGwin et al, 2004), drivers in the current study appeared to be aware of their visual limitations and self-regulated their driving accordingly; those with more restricted fields drove to fewer places (Figure 1c).…”

“…However, our results suggest that vertical field extent may also be an important consideration, especially in turning or curve-taking maneuvers. Previous studies, which have reported an effect of peripheral visual field restriction on driving performance, have either used simulations of severe visual field restrictions on a closed course (Wood et al, 1993;Wood & Troutbeck, 1992, 1995, or have carried out driving simulator evaluations using patients with more restricted fields than the sample in this study (Coeckelbergh et al, 2002;Szlyk et al, 1992). The only study with a similar range of mild to moderately restricted horizontal field extents (130° ± 21°, range 70° -140°) (Szlyk et al, 2002) failed to find any significant correlations between binocular field width and driving performance in a driving simulator.…”

“…Because crashes are rare events, large samples are needed to address questions about visual field extent and driver safety; however, the study of driving performance is more amenable to smaller sample studies. On-road closed-course assessments of driving with simulated binocular field restrictions (Wood et al, 1993;Wood & Troutbeck, 1992, 1994, 1995 and driving simulator assessments of patients with real visual field loss (Coeckelbergh et al, 2002;Szlyk et al, 1992), suggest a relationship between binocular field extent and driving performance even for moderate field loss; however, these approaches do not evaluate the real-world conditions of on-road driving.…”

Driving Simulation in the Clinic: Testing Visual Exploratory Behavior in Daily Life Activities in Patients with Visual Field Defects

“…Patients with visual field defects have been tested before in simulated and real driving settings: Bowers et al 12 and Cockelbergh et al 13 carried out studies in a driving simulator and demonstrated poorer driving performance in patients compared to healthy controls. However they did not record eye-and head-movements and individual differences could not be related to visual exploratory behavior.…”

Simulator-Based Driving with Hemianopia: Detection Performance and Compensatory Behaviors on Approach to Intersections

“…In the real world, however, they may be able to compensate for the loss by exploring the affected (blind) side using head-and eye-scanning. It has been reported that in Holland (where driving with hemianopia is permitted), driving examiners consider increased head-scanning (especially on approach to intersections) to be an effective compensation for peripheral visual field defects (Coeckelbergh et al, 2002). Whether increased head-scanning while driving results in better detection performance has never been quantitatively investigated.…”