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Prevalence of Visual Impairment and Uncorrected Refractive Error – Report from a Canadian Urban Population-based Study


Barbara Robinson, Yunwei Feng, Craig A. Woods, Desmond Fonn, Deborah Gold & Keith Gordon





Ophthalmic Epidemiology


  • The prevalence of visual impairment due to uncorrected refractive error has not been previously studied in Canada. A population-based study was conducted in Brantford, Ontario.

  • The target population included all people 40 years of age and older. Study participants were selected using a randomized sampling strategy based on postal codes.

  • Presenting distance and near visual acuities were measured with habitual spectacle correction, if any, in place. Best corrected visual acuities were determined for all participants who had a presenting distance visual acuity of less than 20/25.

  • Population weighted prevalence of distance visual impairment (visual acuity <20/40 in the better eye) was 2.7% (n = 768, 95% confidence interval (CI) 1.8–4.0%) with 71.8% correctable by refraction. Population weighted prevalence of near visual impairment (visual acuity <20/40 with both eyes) was 2.2% (95% CI 1.4–3.6) with 69.1% correctable by refraction. 

  • Multivariable adjusted analysis showed that the odds of having distance visual impairment was independently associated with increased age (odds ratio, OR, 3.56, 95% CI 1.22–10.35; ≥65 years compared to those 39–64 years), and time since last eye examination (OR 4.93, 95% CI 1.19–20.32; ≥5 years compared to ≤2 years). The same factors appear to be associated with increased prevalence of near visual impairment but were not statistically significant.

  • The majority of visual impairment found in Brantford was due to uncorrected refractive error.

  • Factors that increased the prevalence of visual impairment were the same for distance and near visual acuity measurements.