Risk Factors For Visual Impairment- Report From A Population-based Study (C.U.R.E.S.)

Abstract

Purpose: : Uncorrected refractive error is the leading cause of reversible visual impairment in the world. The prevalence of this problem has not been previously studied in Canada. A population-based study was conducted in Brantford, Ontario and here we report the factors associated with visual impairment.

Methods: : The target population included all people aged 40 years and older in the City of Brantford. Study participants were selected using a cluster sampling strategy based on postal codes. Presenting distance and near visual acuities were measured with the participant’s 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 6/7.5 in either eye. Near visual acuity was assessed binocularly.

Results: : The study population included 768 residents, 39 to 94 years of age; 55.7% were female. Population weighted prevalence of distance visual impairment (visual acuity < 6/12 in the better eye) was 2.7% (95% CI 1.8, 4.0) with 71.8% correctable by refraction. Population weighted prevalence of near visual impairment (visual acuity < 6/12 with both eyes) was 2.2% (95% CI 1.4, 3.6) with 69.1% correctable by refraction. Multivariate analysis by logistic regression showed that the risk of having a distance visual impairment was independently associated with increased age (OR 5.1; 65 or more years compared to those 39 to 64 years), time since last eye examination (OR 4.931; equal or greater than 5 years compared to equal or less than 2 years) and lower educational attainment (OR 1.674; primary school only compared to university). The same factors were associated with the risk of having a near visual impairment but the order of importance differed with educational attainment being the most important (OR 4.643).

Conclusions: : The majority of visual impairment found in the City of Brantford is due to uncorrected refractive error. This finding is similar to what has been found in studies in the United States, the United Kingdom and Australia. Factors that increased the risk of having a visual impairment were the same for distance and near measurements but their relative importance changed.

Keywords: clinical (human) or epidemiologic studies: risk factor assessment • refraction • low vision