AAO 2023: Visual field defects linked to higher risk of car crashes

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For many people, aging can affect the visual field, begging the question, is it still safe to drive? Researchers at the University of Western Australia investigated this question by examining at what point declining vision increases the risk of a car accident.

In this study, which was presented at AAO 2023, the 127th annual meeting of the American Academy of Ophthalmology, the team shared that they found that specific types of defects in an older person’s field of vision are associated with an increased risk of car crashes.

While driving laws vary from state to state in the US, generally, states require drivers to have 20/40 vision or better in at least 1 eye to drive unrestricted. But some studies suggest that other measures of vision, such as visual field, are as important as how well a person sees on the “Big E Chart.”¹

This is because the eye chart tests for our ability to see distant objects clearly while the visual field is how wide we can see when staring straight ahead. This key difference explains why a wide field of vision allows drivers to see enough details on either side of a car while still focusing on the road ahead of them.¹

This is the first population-based investigation to compare a largescale ophthalmic database of visual fields for older adults with police-reported crash, licensing and hospital morbidity data. Researchers evaluated 29 years of data from more than 31,000 drivers in Western Australia aged 50 and older. Over 4,000 older drivers, accounting for 14 percent of older drivers in Western Australia, were involved in at least one car crash. More than half of those in a crash were experiencing some extent of visual field loss.¹

Results suggest that the area of vision affected, and severity of it contributed significantly to crash risk:

• Visual field loss of any sort in both eyes increased the odds of a car crash by 84 percent.
• Moderate visual field loss in one eye increased car crash risk only if it occurred in the left upper or lower quadrants.
• Severe vision loss in any quandrant increased the chances of an accident.
• Central vision loss in either eye was not associated with an increase in car crash incident.

The study’s lead researcher, Siobhan Manners, MD shared how this information can better inform future laws and decisions, saying, “Many people think that only good visual acuity or clarity of vision is necessary for safe driving. We hope these results will help educate the public about the importance of having an adequate field of vision to be able to continue driving safely. We also hope to better inform clinicians, licensing authorities, and people with visual field defects of the thresholds for visual field loss that still allows for safe driving.” ¹

Reference:

1. How Much Vision Loss is Too Much When it Comes to Driving?. American Academy of Ophthalmology. November 6, 2023. Accessed November 6, 2023.