In Western countries, there are no cohorts of childhood refraction data large enough to provide the statistical power to detect subtle genetic effects (e.g. QTL controlling less than 5% of the variation in the trait phenotype). This study will provide complementary information to a moderately sized study (1400 children) in Asia, in which refraction data has been collected, and selected SNP genotyping is planned. This work will also provide preliminary data to inform a future genomewide association studies for refractive error in this cohort.