Cataracts are the leading cause of blindness in the world and account for 15% of blindness in Canada. The condition, which results in deficits in acuity and contrast sensitivity and increased disability glare, is present in half of adults over the age of 65 years. Older drivers with cataract are more likely to have a history of recent driving accidents compared with older drivers without impaired vision, yet it has not been determined whether the surgical removal of cataracts--a highly successful treatment--reduces the likelihood of crashing. Investigators set out to determine the impact of cataract surgery on the crash risk for older adults in the years following surgery, compared with that of older adults with cataracts but who opted not to have surgery.
The prospective cohort study recruited 277 patients aged 55 to 84 with cataract, 174 of whom elected to undergo surgery. Researchers followed the patients for four to six years and compared vehicle crash occurrence involving patients who elected to have surgery versus those who did not.
Results showed that people who underwent surgery were 53% less likely to be involved in a car crash than those who did not have surgery, which translated to five crashes per million miles of travel among recipients of surgery compared to nine crashes per million miles for those who declined surgery. However, the authors, aware of the study's limitations, caution against the inference that surgery can make people better drivers. Patients who opted out of surgery may have had other medical risk factors that influenced both their decision to avoid the procedure and their risk of car crashes. Therefore, while the study may indicate that driving performance of older drivers with cataracts might improve after surgery, the threat of selection bias prevents more firm conclusions.
- Owsley C, McGwin G, Sloane M, et al. Impact of cataract surgery on motor vehicle crash involvement by older adults. JAMA 2002;288:841-9.
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