Development of vision and strabismus in childhood: prevalence and risk factors

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This thesis aimed to investigate the current prevalence of strabismus in Australian children and the impact of various risk factors particularly, admission to Neonatal Intensive Care Units (NICU). In addition, development of vision and ocular motility in infants admitted to NICU was followed-up to explore considerations for an appropriate vision screening guideline for these infants. A systematic review and meta-analysis found a significant decline over time in the prevalence of childhood strabismus globally, with more recent stabilisation to a prevalence of 2.6%. While there were no differences in overall prevalence of strabismus by ethnicity, there was a difference in prevalence by type of strabismus but, the reasons for these differences remain unclear. An analysis on pre-existing data of 7266 children included in the Sydney Childhood Eye Studies of population-based representative samples using gold standard techniques, provided insight into the prevalence of strabismus in Australia and associated risk factors. It was found the prevalence of strabismus increased between 6 months and 17 years of age, with the main contributing factor being significant refractive error. Analysis also found a greater prevalence of anisometropia, myopia and strabismus in children who had been admitted to NICU. This greater risk for eye conditions with admission to NICU was independent of other known risk factors; such as prematurity and low birth weight, indicating a need for ocular screening and surveillance of all children admitted to NICU, beyond those deemed at risk of ROP. The Neonatal Vision Study (NVS) was a prospective longitudinal cohort study of infants admitted to NICU. The majority of infants recruited in the NVS were born premature and of low birth weight. Development of visual acuity (VA) at three months was most highly correlated to corrected age, however by 12 months, the chronological age of the infant was more indicative of mean VA. A large proportion of three month old infants were strabismic on cover test and unable to demonstrate binocular vision however, this is considered to be a result of an immature ocular motor system. By six months postnatal age, the majority of infants were much more testable and outcomes for ocular alignment and ocular motility testing were comparable to those at 12 months of age. This study indicates the appropriate age to provide vision screening for infants admitted to NICU may be at six months, as testability is high and it is early enough to provide intervention for detected conditions.
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