Background: Children with cerebral palsy (CP) often experience visual dysfunction that affects motor function and activities of daily living, but no 'gold standard' classification of visual function has been established. In recent years, however, a valid and reliable Visual Function Classification System (VFCS) for children with CP has been developed.
Aims: To examine the reliability and validity of the Japanese version of the VFCS in individuals with CP.
Methods: The translation of the VFCS was performed according to international standards for the translation of measurements. We conducted questionnaires of professionals (three physicians, eight physical therapists, five occupational therapists, six speech-language-hearing therapists and a certified orthoptist) regarding the content validity of the Japanese version of the VFCS. For reliability and concurrent validity, 148 individuals with CP were classified twice by professionals using the Japanese version of the VFCS, Gross Motor Function Classification System (GMFCS), Manual Ability Classification System (MACS), Communication Function Classification System (CFCS) and Eating and Drinking Ability Classification System (EDACS), with several weeks between each evaluation.
Results: The content validity of the Japanese version of the VFCS almost met the criteria set. The percentage of positive and neutral opinions given by the professionals with regard to the four items ranged from 74% to 92%. The intra-rater reliability was 0.86 (95% CI 0.75-0.96) by Cohen's kappa and 0.93 (95% CI 0.88-0.96) by intraclass correlation coefficient. The inter-rater reliability was 0.67 (95% CI 0.56-0.78) by Cohen's kappa and 0.79 (95% CI 0.69-0.86) by intraclass correlation coefficient. The Spearman correlation coefficients between the VFCS and the GMFCS, MACS, CFCS and EDACS were 0.783, 0.764, 0.738, 0.738 and 0.830, respectively. The concurrent validity was confirmed by the correlations observed with other classification systems.
Conclusions: The results indicated good reliability and validity for the Japanese version of the VFCS.
Keywords: Visual Function Classification System; cerebral palsy; reliability; validity.
© 2023 John Wiley & Sons Ltd.