Visual risk factors for crash involvement in older drivers with cataract

Background: The Impact of Cataracts on Mobility project has previously demo nstrated that older drivers with cataract have an elevated risk of motor ve hicle collision. Objective: To examine what types of visual impairment serve as a basis of t he increased crash risk of older drivers with cataract. Methods and Design: A cross-sectional analysis was performed on 274 Older d rivers with cataract and 103 older drivers free of cataract recruited throu gh 12 eye care clinics for the purposes of the Impact of Cataracts on Mobil ity project, a prospective study on driving mobility in older adults with c ataract. Tests measured visual acuity, contrast sensitivity, and disability glare for each eye separately using habitual distance correction. The depe ndent variable was involvement in at least 1 state-recorded, at-fault vehic le crash during the 5 years prior to study enrollment. Results: Logistic regression evaluated associations (odds ratios [ORs]) bet ween visual function and crash involvement. Better and worse eye models def ined on the basis of visual acuity were developed. Associations between eac h type of visual function and crash involvement were adjusted for age, sex, driving exposure, cognitive status, and other types of visual function. Fo r both the better and worse eye models, contrast sensitivity was independen tly associated with crash involvement, whereas visual acuity and disability glare were not. Drivers with a history of crash involvement were 8 times m ore likely to have a serious contrast sensitivity deficit in the worse eye (defined as a Pelli-Robson score of 1.25 or less) than those who were crash -free (OR=7.86; 95% confidence interval [CI], 1.55-39.79); this association was weaker for the better eye but still statistically significant (OR=3.78 ; 95% CI, 1.15-12.48). Crash-involved drivers were 6 times more likely to h ave severe contrast sensitivity impairment in both eyes (OR=5.78; 95% CI, 1 .87-17.86) than hash-free drivers. A severe contrast sensitivity deficit in only 1 eye was still significantly associated with crash involvement (OR=2 .70; 95% CI, 1.16-6.51). Conclusion: Severe contrast sensitivity impairment due to cataract elevates at-fault crash risk among older drivers, even when present in only 1 eye.