Visual motor development in full term and preterm infants
Abstract: Smooth tracking and efficient reaching for moving objects require the ability to predict the velocity and trajectory of the object. This skill is important to be able to perceive human action and object motion in the world. This thesis explores early visual motor development in full term and preterm infants.Study I showed that horizontal eye tracking develops ahead of vertical (full term infants at 5, 7 and 9 months of age). The vertical component is also more affected when a second dimension is added during circular pursuit. It is concluded that different mechanisms appear to underlie vertical and horizontal eye movementsStudy II-IV compared the development of the ability to visually track and reach for moving objects in very preterm infants born <32 gestational weeks to healthy infants born at term. The development of horizontal smooth pursuit at 2 and 4 months of corrected age was delayed for the preterm group (Study II). Some infants were catching up whereas others were not improving at all. A question raised by the results was whether the delay was caused by specific injuries as a result of the prematurity. However, the delays persisted when all infants with known neonatal complications and infants born small for gestational age were excluded (Study III), indicating that they were caused by prematurity per se. At 8 months corrected age preterm and full term infants were equally good at aiming reaches and successfully catching a moving object. Nevertheless, the preterm group used a bimanual strategy more often and had a more jerky and circuitous path than the full term group (Study IV). In summary, preterm infants showed a delayed visual motor development compared to infants born at term.The results of these studies suggest that there is additional diffuse damage to the visual motor system that is not related to neonatal complications as diagnosed today. Measuring smooth pursuit could potentially be a new method for early non-invasive diagnosis of impaired visual function.
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