Aims: To establish, using the crowded Kay Picture test, the ranges of visual acuity in children aged 42–48 months which are associated with normal and abnormal refractive status. To identify the visual acuity and refractive error distribution in this age group. Methods: Children attending a primary vision screening service had visual acuity measured and cycloplegic refraction undertaken. Refractive error was pre-defined as normal, borderline and abnormal by using existing evidence. On the basis of the refractive error found, visual acuity ranges associated with each refractive group were established. Children with squint and ocular pathology were excluded. Results: Seven hundred and thirty-three children participated, with a median age of 43 months. Ninety per cent had a normal monocular refractive error. Ninety-three per cent of children had insignificant anisometropia. When anisometropia was insignificant, the median (IQR) visual acuity was 0.05 (0.00–0.10) for both right eye and left eye. Median (IQR) interocular visual acuity difference in this group was 0.025 (0.00–0.05). There was a statistically significant difference between the visual acuity ranges for each of the normal, borderline and abnormal refraction groups ( p < 0.001). The median refractive error was þ0.38D spherical equivalent for the right eye and þ0.50D spherical equivalent for the left eye. Conclusion: Children of 42–48 months with monocular visual acuity of equal to or better than 0.10 and with an interocular visual acuity difference of 0.05 or less when tested with the crowded Kay Picture test are likely to have a normal refractive status.