Pilot study of an auditory scanning reminder system for drivers with hemianopia

Abstract

Purpose : Drivers with hemianopic field loss (HFL) can compensate for their vision loss by scanning toward the blind side. However, prior studies suggest they often do not scan far enough, especially at intersections where a wide field has to be viewed. To address this problem, we developed a system to give lateralized auditory scanning reminders when there was a failure to make a sufficiently large head scan toward the blind side. Here we report the results of a pilot study to evaluate the effects of the system on scanning and detection when approaching intersections in a high fidelity simulator.

Methods : To date, 7 subjects with HFL have completed 2 drives with and 2 drives without the system while head and eye movements were tracked with a 6-camera remote tracker. They drove along city routes directed by GPS navigation instructions with 35 intersections per drive and pressed the horn as soon as they detected a motorcycle. Of 15 motorcycles in each drive, 10 appeared at four-way (+) intersections approaching from the right or left on a collision course. The system monitored head movements from 60 to 30m before the intersection and triggered an audio-cue reminder at 30m if the driver did not make a head scan of at least 20° to the blind side. This threshold was the minimum head scan magnitude needed to predict early detection of motorcycles derived from prior data using a machine learning classification tree. The cue was a single tone (1s) from a directional speaker at about 45° on the blind side.

Results : The proportion of head scans which did not meet the 20° threshold decreased by 30% (range 10% to 50%) for drives with the system compared to drives without the system. The system significantly improved response times to motorcycle hazards approaching from the blind side (mean decrease of 678 ms, p = 0.011) but had no significant effect on response times to motorcycles from the seeing side. All participants found the system to be helpful and stated they would definitely want to use the system in their own car.

Conclusions : Our preliminary results suggest the scanning reminder system had a positive effect on scanning behaviors such that drivers with HFL made more sufficiently large head scans toward the blind side when approaching intersections. The increased number of sufficient head scans and decreased hazard response times may result in lower risk for collisions at intersections.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.