Binocular visual field impairment in glaucoma and at-fault motor vehicle collisions.

PURPOSE

To evaluate the association between the binocular visual field defects in drivers with glaucoma and the risk of motor vehicle collision (MVC) involvement.

METHODS

A retrospective cohort study was conducted on 438 drivers with glaucoma aged 55 years or older using data from 1994 through 2000. Demographic, clinical, and driving characteristics were obtained from chart abstractions and patient survey. Binocular field measures were generated by combining data from the monocular (central 24-degree radius) fields whereby the binocular field measure was defined as the more sensitive point at each monocular field location. Measures included threshold (TH), total deviation (TD), and pattern deviation (PD); severe impairment in these measures was defined as falling into the worst quartile. MVC data were obtained from police records. Rate ratios (RR) and 95% confidence intervals (CI) were calculated.

RESULTS

Drivers with severely impaired PD measures were twice as likely to have an at-fault MVC compared with those not severely impaired (RR, 2.13; 95% CI, 1.21-3.75); those with severely impaired TH (RR, 1.49; 95% CI, 0.81-2.74) and TD (RR, 1.50; 95% CI, 0.82-2.74) also had an increased rate of at-fault MVCs, although these were not significant. When the binocular central visual field was stratified into 9 regions, drivers with impaired TH, TD, or PD had similarly elevated MVC rates in all regions compared with those not severely impaired, though not all reached statistical significance.

CONCLUSIONS

On the basis of clinical measures of visual field routinely used in the management of glaucoma, drivers with glaucoma with severe PD field defects in the binocular field have a higher rate of at-fault MVC compared with those with less impaired or unimpaired binocular visual fields.