Incidence of visual impairment in Canada: the Canadian Longitudinal Study on Aging.

OBJECTIVE

Determine the 3-year incidence of visual impairment (VI) in Canada and its risk factors.

DESIGN

Prospective 3-year cohort study PARTICIPANTS: Data from 23 973 adults taking part in the Canadian Longitudinal Study on Aging Comprehensive Cohort baseline and 3-year follow-up exams were included.

METHODS

Inclusion criteria were 45 to 85 years of age, community-dwelling, and living near one of the 11 data collection sites across 7 Canadian provinces. Presenting binocular visual acuity was measured using the Early Treatment of Diabetic Retinopathy study chart. Incidence of VI was defined as the development at follow-up of visual acuity worse than 20/40 in those with acuity better than or equal to 20/40 at baseline.

RESULTS

3.88% (95% confidence interval [CI] 3.61-4.17) of Canadian adults developed VI over a 3-year period. There was a high degree of variability in the incidence between Canadian provinces with a low of 1.42% in Manitoba and a high of 7.33% in Nova Scotia. Uncorrected refractive error was the leading cause. Risk factors for incident VI included older age (odds ratio [OR] = 1.07, 95% CI 1.06-1.07), Black race (OR = 2.64, 95% CI 1.36-5.14), lower household income (OR = 1.73 for those making less than $20,000 per year, 95% CI 1.24-2.40), current smoker (OR = 1.78, 95% CI 1.37-2.32), and province.

CONCLUSION

The incidence of visual impairment is common in older Canadian adults, varies markedly between provinces, and is largely owing to treatable causes. Risk factors for VI suggest subgroups that may benefit from interventions to improve access to eye care.