| Summary: | Intermittent Exotropia [X(T)], is a common form of childhood strabismus. Clinical decision making for this condition is hampered by lack of evidence from well designed prospective studies. This thesis consists of five papers authored by myself and my collaborators, and a linking statement placing these papers in a scientific context. The first two papers describe the development and clinical utility of a novel scoring system for the control of X(T), which can be used to assess the progress of the condition and the effect of treatment on this parameter. This scoring system, the Newcastle Control Score for Intermittent Exotropia, consists of a parent/carer reported 'Home' component and an objective, 'Clinic', assessment of the ease of realignment of the exotropia in response to disruption of fusion by a cover test. The second two papers describe the establishment of relevant age related normal ranges of a new test of distance stereoacuity, the Frisby Davis Distance Stereotest (FDiffi ), and the application of this test to a cohort of children with X(T). In contrast to previous studies, we found an 'all or none' pattern of distance stereoacuity in X(T), rather than a gradual decline in distance stereoacuity. The final paper describes the initial results of a prospective study of a cohort of 460 children with X(T), recruited in 26 centres, which examined their clinical phenotype and management in the first year following recruitment. The striking finding of this study was that over half the children in the cohort received no treatment in the first year after diagnosis, suggesting that decision making by professionals in this condition was hampered by a lack of evidence about natural history and treatment outcomes. The linking statement concludes with a brief description of related and ongoing research by our group and others.
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