Refractive error, IQ and reading ability: a longitudinal study from age seven to 11.

Children from a population sample whose cycloplegic refractive errors included myopia, pre-myopia and hypermetropia were compared on measures of IQ and reading with a group of children without significance refractive errors. At age 11 both those with myopia and with pre-myopia had increased verbal and performance IQ, while those with hypermetropia had slightly reduced verbal and performance IQ, in comparison with the children without refractive errors. The differences in verbal IQ were not attributable simply to earlier differences, but the differences in performance IQ were attributable to earlier differences. No significant differences in reading scores were found at either age. It is concluded that differing abilities of myopic and other children at age 11 are not fully explained by differences in family background or in pre-existing ability.