Conclusions for or against services are invalid without appropriate research evidence

EDITOR—Rahi and Dezateux highlighted the current dilemma about preschool vision screening.1 A systematic review has detailed the lack of published evidence on whether the target conditions (amblyopia, non-obvious squint, and refractive error) are disabling and whether detection at preschool age results in better treatment outcomes than detection at school age.2

The review concludes that published hard evidence is lacking on preschool vision screening but then recommends that providers consider discontinuing current programmes. Without appropriate high quality research evidence, conclusions either in favour of or against these services are equally invalid. Ongoing research into this subject has occurred within a multidisciplinary birth cohort study of 14 000 children born in Avon between April 1991 and December 1992.3 A randomised controlled trial of screening methods for ocular defects in children under 3 years of age has collected data on whether any disability in social, physical, or cognitive function is associated with the target defects at the age of 41/2 years. 4 5 The birth cohort study aims to complete a detailed, multidisciplinary assessment of all 14 000 children at the age of 7 years, half of whom will have had preschool vision screening while the other half will have not. This will provide high quality data on whether the target defects are associated with suboptimal performance in other areas of life at this age and, if so, whether preschool screening resulted in a better outcome (visual, educational, or developmental) than screening at school age. As stated in the review,2 these data are necessary to decide whether to support preschool vision screening.

The review's recommendations lack …