Background <p>Optical coherence tomography (OCT) has been of great importance in the diagnostics and follow-up of many retinal diseases the last 25 years. More recently, this technology has also proved useful in the evaluation and follow-up of various neurological and psychiatric disorders. Also, certain prenatal impacts, such as prematurity and foetal alcohol spectrum disorder have shown abnormal findings on OCT. The aim of this study was to examine children that have been prenatally exposed to opioid maintenance therapy (OMT) with OCT.</p> Methods <p>As a part of a comprehensive study on visual and visual-motor function, 63 children aged 5–13 years exposed prenatally to OMT and 77 age-matched controls were examined with OCT, collecting data from the peripapillary retinal nerve fibre layer (RNLF) and the macular region. The participants were recruited at two different centres with different OCT-instruments.</p> Results <p>A highly significant thinning of the peripapillary RNFL was found in the OMT-exposed children compared to the controls at both study centres. The macular data did also show a reduced retinal thickness and volumes in several macular regions in the OMT-exposed children, but to a variable degree at the two participating study centres. The reasons for this variability remain uncertain. There was no correlation between the OCT data and visual acuity.</p> Conclusions <p>This is the first study reporting OCT-data from children prenatally exposed to OMT. The significant thinning of the peripapillary RNFL in the OMT-exposed children most probably reflects a negative impact of the opioid substances on the foetal neurodevelopment. Further OCT-studies on OMT-exposed children should be carried out.</p>