Thirty-one patients with optic nerve hypoplasia (ONH) or septo-optic dysplasia and two patients with segmental ONH underwent retinoscopy. The results were compared with those of 20 normal subjects. There was a higher prevalence of astigmatism in the patients than in the controls. Two patients with segmental ONH had no evidence of astigmatism. The association of astigmatism with ONH has not hitherto been reported. The close association of ONH with astigmatism highlights the importance of performing careful retinoscopy in children with ONH or septooptic dysplasia in order to identify and correct errors of refraction, thereby optimising visual function and diminishing the likelihood of the development of superadded amblyopia.