Quality of Life and Visual Function in Children with Intellectual Disabilities

Questionnaires have been developed to allow assessment of latent traits in patients, such as self-perception of health-related quality of life (HQoL) and vision-related quality of life (VQoL), which have not been investigated in a population of children with intellectual disability (ID). This thesis aims to address this knowledge gap by conducting a study on developing an instrument to investigate HQoL and VQoL in children with ID.Since the instruments applied in the present study were previously validated in children with normal development, the first part of the thesis re-evaluates the psychometric properties of the adapted instruments used for self-perceived HQoL and VQoL and proxy HQoL and VQoL. The construct of subjective perceptions of quality of life is established by identifying the domains of HQoL and VQoL in children with ID. As part of the validation process, Rasch analysis is used to reduce redundant items and to refine the scaling, thus, increasing the validity and internal consistency of the instruments. A validated instrument is then applied to the subgroups of the study and revealed that there is significantly lower value in the perception of HQoL in children with ID than those without ID, but no difference identified in VQoL. The objective assessment of vision screening demonstrates the fact that children with ID have a higher risk of visual abnormalities. However, visual abnormality does not indicate significant impact on HQoL and VQoL as evidenced in the survey in children with ID. The proxy responses from parental carers are compared to childrens subjective views of their HQoL and VQoL. As predicted, the results from parents and children are not strongly associated