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E.S. Van de Graaf, G.W. van der Sterre, H. van Kempen, C.W. N. Looman, J.–R. Polling, H.J. Simonsz; Factor–analysis of the Amblyopia and Strabismus Questionnaire (A&SQ) . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5705.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: After the development and the clinical validation (ARVO, 2004) of the Amblyopia & Strabismus Questionnaire (A&SQ), factor–analysis was needed to prove that the scores of the A&SQ were related to the underlying quality of life. Methods: The factor–analysis, Principal Components Analysis on the correlationmatrix (PCA) was applied to the A&SQ outcomes, after implementing imputation steps to get numerical values for all questions. The A&SQ comprised five domains, formulated into 26 questions: fear of losing the better eye, problems with distance estimation, visual disorientation, diplopia, problems with social contact and cosmetic problems. It had been filled out by healthy controls (N=53), a historic cohort of patients treated for amblyopia 30 years ago (N=174), and patients from our outpatient clinic (N=68). The PCA scored and grouped the quality of life questions by considering the mutual correlations of the answers given. The first set of scores represented the overall quality of life and the second set was extracted to distinguish between the different domains. Results: 33.12% of the variance was explained by the overall quality of life. The second proportion explained 9.07% of the variance. When taking this into account, most of the questions were grouped within the five domains, and the domains were well separated from each other. The questions about fear of losing the better eye were at the one end of the range of scores and related to difficulties caused by having only one good eye. The questions about diplopia were at the other end and concerned difficulties caused by having one good and one bad eye. The questions about the problems with distance estimation and visual disorientation were nearer to the end that related to having one good and one bad eye. The questions about problems with social contact and cosmetic problems were near the end that related to having only one good eye. Conclusions: Factor–analysis demonstrated that the questions in the A&SQ accurately measured the quality of life of amblyopia and/or strabismus patients.
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