Relationship between Subjective Driving Concerns and Objective Driving Performance on a Simulator in Patients with Glaucomatous Visual Field Loss

Abstract

Purpose : Patients with visual impairment may limit their driving exposure due to concerns about their ability to drive safely. However, many patients continue to drive despite potential risky driving behavior. The purpose of this study was to investigate the relationship between subjective concerns about driving ability in patients with glaucoma and their objective performance assessed in a driving simulator.

Methods : This was a cross-sectional study involving 77 patients with bilateral glaucomatous visual field loss and 86 control subjects. Mean age was similar in the two groups (67 ± 12 vs. 64 ± 10 years, respectively; P=0.090). A latent variable representing subjective driving concerns was extracted through Rasch analysis of a standardized questionnaire. Objective driving performance was evaluated on a driving simulator with curve negotiation and car following tasks. A summary index of driving performance was extracted through principal component analysis of simulator data. Abnormal results were determined if they exceeded the 95% limits of normality as determined from the control group.

Results : Patients with glaucoma were significantly more concerned about their ability to drive compared to control subjects (28.7 ± 24.8 vs. 19.3 ± 18.5; P=0.007). Objective driving performance was significantly worse in glaucomatous than controls (21.4 ± 14.6 vs. 14.6 ± 7.9; P<0.001). Objective driving performance was also significantly worse in subjects with history of at-fault motor vehicle crashes versus those without (26.1 ± 28.2 vs. 17.3 ± 10.2; P=0.032). There was a significant relationship between subjective driving concerns and objective performance (R²=11%; P<0.001). However, from the 17 glaucoma patients with significant driving concerns, only 4 (24%) had clear evidence of unsatisfactory objective driving performance. From the 14 glaucoma patients deemed unfit to drive on simulator testing, 10 (71%) did not have significant driving concerns.

Conclusions : There is substantial disagreement between subjective driving concerns and objective driving performance in glaucoma subjects. Many patients with glaucoma may continue to drive despite objective evidence of unsatisfactory driving performance.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.