Visual processing impairment and risk of motor vehicle crash among older adults.

Context: Motor vehicle crash risk in older drivers has been associated with visual acuity loss, but only weakly so, suggesting other factors contribute. The useful field of view is a measure that reflects decline in visual sensory function, slowed visual processing speed, and impaired visual attention skills.
Objective: To identify whether measures of visual processing ability, including the useful field of view test, are associated with crash involvement by older drivers.
Design: Prospective cohort study with 3 years of follow-up, 1990-1993.
Setting: Ophthalmology clinic assessment of community-based sample.
Patients: A total of 294 drivers aged 55 to 87 years at enrollment.
Main Outcome Measure: Motor vehicle crash occurrence.
Results: Older drivers with a 40% or greater impairment in the useful field of view were 2.2 times (95% confidence interval, 1.2-4.1) more likely to incur a crash during 3 years of follow-up, after adjusting for age, sex, race, chronic medical conditions, mental status, and days driven per week. This association was primarily mediated by difficulty in dividing attention under brief target durations.
Conclusion: Reduction in the useful field of view increases crash risk in older drivers. Given the relatively high prevalence of visual processing impairment among the elderly, visual dysfunction and eye disease deserve further examination as causes of motor vehicle crashes and injury.