The Development and Treatment of Strabismic Amblyopia

Background: Strabismus development is a complex process involving various parts of the visual system. This complexity is increased by the presence of numerous subtypes. Although research has shown strong genetic and environmental components it is not yet clear if there are stronger associations with particular subtypes. In addition, the association between strabismus and retinal development and its limitation on visual outcome, in combination with other factors such as compliance to treatment, has not yet been explored. Methods: Strabismic subjects were recruited to four areas to assess the development and treatment of strabismic amblyopia. Genetic and environmental factors were systematically identified within the literature and through strabismic pedigrees. The influence of strabismic development on the retina was assessed using optical coherence tomography (OCT) in strabismic infants compared to healthy controls. OCT and electronic monitors were used to investigate causes of poor outcomes after amblyopia treatment. Results: Systematic reviewing of the literature revealed strong associations between strabismus and various environmental and genetic factors. By observing the inheritance of strabismus through pedigrees it was observed that accommodative forms of esotropia had a stronger association with inheritance than other subtypes. The effect of strabismus on retinal development revealed delayed or abnormal changes within particular layers of the retina. These defects were observed in both eyes of strabismic subjects and were sustained in subjects who failed to reach successful outcomes after treatment. In addition, through using electronic monitors, compliance to both glasses wearing and occlusion were significantly correlated to visual outcomes. Conclusion: This thesis continues to support growing evidence that both genetic and environmental factors play a role in strabismus development. Its development also has retrograde effects on the visual pathway in particular the retina, which is sustained unless treatment is successful. In addition, compliance to treatment has shown to be vital in obtaining a successful outcome.