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J. Khadka, J. M. Woodhouse, B. Ryan, T. Margrain; Development of the Cardiff Visual Ability Questionnaire for Children and Young People. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4722.
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Our aim was to develop an instrument to measure vision-specific ability in children and young people with a visual impairment. Such a tool would be useful to assess efficacy of rehabilitative interventions in this demographic.
89 items on a six scale response category were developed from 13 focus groups conducted with children and young people with and without a visual impairment. The 89-item instrument was piloted on 45 visually impaired children and young people (64% boys and 36% girls; mean age, 12.6+/- 3.5 yrs; median, 13 yrs) using face-to-face interviews. All participants were between 5 and 18 years of age, verbally communicating and had some vision. Ethical approval was obtained and parental and individual consent were obtained prior to an interview. Rasch analysis was used to analyse the response category function and to facilitate item removal whilst ensuring a valid unidimensional scale.
64 items were removed primarily on the basis of infit statistics, outfit statistics and/or missing data. The final 25-item Cardiff Visual Ability Questionnaire for children and young people (CVAQC) had good infit and outfit values (infit: 0.80-1.18, outfit: 0.83-1.25), good person and item separation (>2) and high person and item reliability coefficients (0.82 and 0.94 respectively). Rasch analysis identified disordered category thresholds and under utilization of the end-response category. Therefore, categories were merged to a four-response option.
We have developed a robust 25-item, 4 response category CVAQC which works together to form a unidimensional scale for the assessment of efficacy of rehabilitative interventions on children and young people with visual impairment.Key words: Children and young people, Visual impairment, CVAQC, RASCH analysis
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