Development and Psychometric Evaluation of the Functional Vision Scale for Adults

Objective: This study aimed to develop and psychometrically evaluate the Functional Vision Scale for Adults (FVSA), an occupation-centred patient-reported outcome measure on daily functioning across key occupational performance domains. Methods: The scale development process followed incorporating a comprehensive literature review and expert consultations (n = 10) to establish content validity. An initial item pool of 51 items was refined through expert review and pilot testing (n = 55), resulting in a 33-item scale. The final version was administered to 526 adults (372 without visual problems, 154 with visual problems). Construct validity was evaluated using exploratory and confirmatory factor analysis. Known-group validity was assessed by comparing scores between participants with and without visual problems. Reliability was tested through internal consistency (Cronbach's α, McDonald's ω) and test-retest reliability (ICC) in a subsample (n = 62). Results: Exploratory and confirmatory factor analyses supported a four-factor structure corresponding to education, activities of daily living (ADLs), social participation and instrumental ADLs (IADLs). Known-group validity was confirmed with statistically significant differences across all subscales (p < 0.05). The FVSA Total Score demonstrated excellent reliability, as evidenced by a strong ICC value (ICC = 0.835, p < 0.001) supported by high internal consistency coefficients (ω = 0.946; α = 0.933). Conclusions: The FVSA is a reliable and valid instrument that provides a comprehensive, occupation-centred assessment of functional vision in adults.