Abstract
Purpose:
Glaucoma is the second leading cause of vision loss among the elderly in the U.S. Motor vehicle collision (MVC) rates in the U.S. increase sharply in drivers aged 70 and older. Despite its significance, there have been conflicting reports about whether glaucoma is associated with higher MVC rates. This study investigated whether older drivers with glaucoma have a higher MVC rate as compared to those without glaucoma.
Methods:
The study was based on a population-based sample of 2000 licensed drivers aged 70 years and older who reside in north central Alabama. At-fault MVC involvement for five years prior to enrollment was obtained from state records. Three aspects of visual function were measured: habitual binocular distance visual acuity, binocular contrast sensitivity and the binocular driving visual field constructed from combining the monocular visual fields of each eye (Huisingh et al., 2014). General cognitive status was assessed with the mini-mental status examination (MMSE). Glaucoma was confirmed by medical records.
Results:
Drivers with glaucoma (n = 206) had a 1.65 (95% CI 1.20-2.28, p < 0.01) times higher MVC rate compared to those without glaucoma even after adjusting for age, gender and MMSE. Among drivers with glaucoma, visual field loss was more strongly associated with higher MVC rates (RR=2.48, 95% CI 1.28-4.82, p < 0.01) compared to deficits in visual acuity (RR = 1.95, 95% CI 0.70-5.43, p = 0.20) and contrast sensitivity (RR = 0.37, 95% CI 0.13-1.08, p = 0.07). When the visual field was divided into six sub-regions (upper, lower, left, and right visual fields; horizontal and vertical meridians), left side visual field loss was most strongly associated with higher MVC rates (RR = 3.04, 95% CI 1.54-5.97, p < 0.01) compared to the horizontal, upper, lower and right side visual field loss. There was, however, no association between deficits along the vertical meridian and higher MVC rates (RR = 1.20, 95% CI 0.61-2.38, p = 0.59).
Conclusions:
Findings suggest that older drivers with glaucoma are more likely to have a higher MVC rate than those without glaucoma. Impairment in the driving visual field appears to contribute most to this increased MVC rate as compared to impaired visual acuity and contrast sensitivity, highlighting the importance of clinicians discussing driving safety with glaucoma patients, particularly those with visual field defects.