The effects of neonatal hypoglycaemia on vision and global motion processing in two-year-old children

Abstract

BACKGROUND: Retrospective studies have demonstrated that severe neonatal hypoglycaemia can cause abnormal visual development, but the effects of moderate hypoglycaemia on vision and visual processing are unknown. It has been proposed that the dorsal visual stream is vulnerable to developmental disorders. Therefore functions mediated by this cortical visual pathway could be potential markers for any effects that moderate hypoglycaemia may have on cortical visual development. The research in this thesis was part of the Children with Hypoglycaemia and their Later Development (CHYLD) study, which was established to prospectively investigate the neurodevelopmental effects of neonatal hypoglycaemia at two and 4.5 years of age. This thesis focuses on vision and on global motion processing, a function of the dorsal visual stream, at two years of age. OBJECTIVES: 1. To develop and validate a method of assessing global motion coherence thresholds suitable for use with two‐year‐old children. 2. To investigate the effects of neonatal hypoglycaemia (<2.6mmol/L blood glucose in the first 48 hours of life) on vision and global motion processing. METHODS: A novel method of measuring motion coherence thresholds, an index of global motion processing, was validated on healthy adults and children aged between 21‐ and 27‐months. The method utilised the optokinetic reflex. Vision screening and measurement of global motion processing were carried out on 403 two‐year‐old children enrolled in the CHYLD study who were born at risk of neonatal hypoglycaemia. RESULTS: The novel method of assessing global motion processing was repeatable and highly successful for testing two‐year‐old children. Associations were found between motion coherence threshold, stereopsis, and motor function. Results from the CHYLD study cohort indicated that neonatal hypoglycaemia had no clinically significant impact on unaided vision, stereopsis, manifest refractive error, prevalence of ocular anomalies, or motion coherence threshold at the age of two years. CONCLUSIONS: Global motion processing can be measured in two‐year‐old children using the method developed by this study. The relationships among global motion processing, stereopsis and motor function that were found are consistent with the current view that the dorsal stream is involved in visuomotor coordination. Moderate neonatal hypoglycaemia, when managed appropriately, was not associated with poorer visual outcomes or poorer global motion processing.