Aged Drivers May Experience Decreased Visual Function While Driving

To investigate conventional visual acuity (VA) and changes therein over time in older drivers.

A cross-sectional study.

One hundred twenty-four drivers (41 younger drivers aged 21-39 years, 40 middle-aged drivers aged 40-59 years, and 43 older drivers aged 60-77 years) who consented to undergo conventional and functional VA testing, perform the Trail Making Test B, and complete a questionnaire on visual performance while driving at an expressway rest stop in Ashigara, Japan, were studied.

The overall proportion of the study subjects with a decimal bilateral VA less than 0.7, the Japanese threshold score for obtaining and renewing a driver's license, was 10%. The number of the subjects with decimal functional VA scores and minimum VA scores less than 0.7 was significantly higher in the older group than in the younger group (P < 0.05), although the conventional VA scores did not differ significantly between the older and younger groups (P = 0.621). The Trail Making Test B scores were significantly higher in the older group than in the younger and middle-aged groups (P < 0.05). The total score of the "visual performance during driving at night" category correlated significantly with the logMAR functional VA and logMAR minimum VA (P < 0.05) but not the logMAR VA.

Older drivers might experience decreased functional VA and increased frequency of transient decreases in VA while driving. The functional VA test might capture visual impairment among older drivers that went undetected by the conventional VA test.