We were interested to read the paper by Fotouhi and colleagues, on the prevalence of refractive errors in schoolchildren in Iran,1 in which the authors used cycloplegic autorefraction for children aged 7–15 years and non-cycloplegic autorefraction for children aged 15–18 years. This paper illustrates the well-recognised need for cycloplegia in order to obtain accurate refractive estimates in children up to at least age 12.2 However, the use of cycloplegia may reduce compliance and may not be possible in some situations—for example, studies of general child development such as the 1958 and 1970 national cohort studies in the UK. In such situations, other measures such as visual acuity may be used to infer the presence, but not the type of refractive …