Neurological

Audible signals encourage proactive scanning for drivers with homonymous hemianopia

In certain jurisdictions, people with hemianopia of the same name (HH) are allowed to drive. According to a study published in JAMA Ophthalmology, drivers with this condition may be able to compensate for loss of half-field vision by scanning towards the blind side using eye and head movements.

According to the report, “previous research suggests that sometimes drivers with HH do not scan or not scan far enough when approaching an intersection to scan the blind side, resulting in impaired response to danger.”

Between October 2018 and May 2019, the researchers conducted a cross-sectional study using a driving simulator for a single visit in a visual rehabilitation research laboratory. They included a voluntary sample of people with HH with no visual neglect in the analysis.

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Participants finished trips with and without the scanning of reminder cues (a single tone from a speaker on the blind side), the report said. Scanning was quantified by the percentage of intersections that had a previous large scan (a scan with head movement of at least 20 °, taken 30 meters from the intersection). The reactions to motorcycles were quantified over the time to the first restraint and the time to the sound of the horn.

A total of 16 participants completed the study, but 2 were excluded from the analysis. Data of the remaining 14 participants (median [IQR] Age, 54 [36-66] Years and 13 men [93%]) were included. Investigators found that stroke was the main cause of HH (10 participants [71%]). They also found that 6 participants (43%) had right-sided HH.

Participants were more inclined to perform an early large scan to the blind side when driving with clues than when driving without clues (65% vs. 45%; difference 20%). [95% CI, 5%-37%]; P <.001). When participants did an early large blind side scan, they were quicker to first get restrained on motorcycles on the blind side (mean [SD], 1.77 [1.34] versus 3.88 [1.17] Seconds; Difference, -2.11 [95% CI, −2.46 to −1.75] Seconds; P <.001) and faster to sound the horn (medium [SD], 2.54 [1.19] against 4.54 [1.37] Seconds; Difference, -2.00 [95% CI, -2.38 to -1.62] Seconds; P <.001) as if they did not do an early scan.

The study reports several limitations. For one thing, the sample size is relatively small and heterogeneous. Detection was also investigated in relatively simple motorcycle driving scenarios and response times were based on horn presses rather than braking responses.

“This post-hoc analysis suggests that audible reminders can encourage proactive scanning, which can be linked to faster responses to hazards,” the researchers said. “This hypothesis should be taken into account in future prospective studies.”

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Xu J, Emmermann B, Bowers AR. Acoustic reminders to encourage proactive scanning when approaching intersections for drivers with hemianopia of the same name. JAMA Ophthalmol. Published online November 24, 2021. doi: 10.1001 / jamaophthalmol.2021.5007

This article originally appeared on Ophthalmology Advisor

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