Refractive Error Study in Children: Sampling and measurement methods for a multi-country survey

PURPOSE: The Refractive Error Study in Children was designed to assess the prevalence of refractive error and vision impairment in children of different ethnic origins and cultural settings. METHODS: Population based cross-sectional samples of children 5 to 15 years of age were obtained through cluster sampling. Presenting, uncorrected, and best-corrected visual acuity, along with refractive error under cycloplegia, were the main outcome measures. Amblyopia and other causes of uncorrectable vision impairment were determined, RESULTS: Study design and sample size calculations, survey enumeration and ophthalmic examination meth ods, quality assurance monitoring, and data analyses and statistical methods are described. CONCLUSIONS: The study design, sample size, and measurement methods ensure that the prevalence of age-specific and sex-specific refractive error can be estimated with reasonable accuracy in the target populations. With commonality of methods, a comparison of findings between studies in different ethic origins and cultural settings is possible. (Am J Ophthalmol 2000;129:421-426. (C) 2000 by Elsevier Science Inc. All rights reserved.).