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B. E. Robinson, Y. Feng, C. A. Woods, D. Gold, K. Gordon, D. Fonn; Canadian Uncorrected Refractive Error Study - A Pilot Study. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1718.
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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 pilot study was conducted in Brantford, Ontario. The primary purpose of this cross-sectional study was to measure the prevalence of uncorrected refractive error in a representative sample of the population.
The target population included all people 40 years of age 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.
The study population included 768 residents 39 to 94 years of age; 55.7% were female. One hundred and twenty-six participants or 16.4% (95%CI, 13.7% to 19.5%) were found to have presenting distance visual acuity less than 6/7.5 in their better seeing eye (75 female, 51 male). Nearly 3% of the sample had a presenting distance visual acuity in the better eye that was less than 6/12, (95%CI, 1.7% to 4.43%). Best corrected visual acuities improved by 1 to 5 lines for 89 of these 126 study participants (70.63%). In addition, 203 study participants, 26.43% (95%CI, 23.12% to 29.9%), were found to have presenting near visual acuity less than 6/7.5. Near visual acuity was improved with a new spectacle correction for 156 or 76.85% of these study participants.
There is a high prevalence of uncorrected refractive error in the City of Brantford. This finding is similar to what has been found in studies in the United States, the United Kingdom and Australia. The majority of people with decreased distance and near visual acuities can be corrected with new spectacles. Decreased near visual acuity occurred 61% more frequently than decreased distance visual acuity in this population.
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