PURPOSE: To evaluate the association between visual field defects in the central 24 degrees field and the risk of motor vehicle collisions (MVCs) among patients with glaucoma. METHODS: A nested case-control study was conducted in patients with glaucoma aged 55 or more. Cases were patients who were involved in a police-reported motor vehicle collision (MVC) between January 1994 and June 2000; controls were those who had not experienced an MVC at the time of their selection. For each patient, an Advanced Glaucoma Intervention Study (AGIS) score was calculated on automated visual fields collected with the 24-2 or 3-2 programs. RESULTS: With respect to the better-eye AGIS score, compared with patients with no visual field defect, those with severe defects (scores 12-20) had an increased risk of an MVC (odds ratio [OR] 3.2, 95% CI 0.9-10.4), although the association was not statistically significant. Moderate (6-11) or minor field defects (1-5) in the better eye were not associated with the risk of involvement in a crash. In the worse eye, patients with moderate or severe field defects were at significantly increased risk of an MVC (OR 3.6, 95% CI 1.4-9.4 and OR 4.4, 95% CI 1.6-12.4, respectively) compared with those with no defects. Minor field defects in the worse eye did not increase risk of MVC (OR 1.3, 95% CI 0.5-3.4). CONCLUSIONS: Patients with glaucoma who have moderate or severe visual field impairment in the central 24 degrees radius field in the worse-functioning eye are at increased risk of involvement in a vehicle crash.