Exploratory factor analysis as a validation tool in a questionnaire to evaluate the uptake of cataract surgery

Background Exploratory Factor Analysis (EFA) evaluates construct validity by identifying underlying relationships among questionnaire items, helping determine the number of latent constructs. This study aimed to validate a newly developed questionnaire on cataract surgery uptake among the community by interviewing subjects aged 50 years and older.   Methods A bilingual questionnaire, based on theoretical factors of knowledge, perception, attitude, and practice, was developed through literature review and expert interviews. It underwent forward-backward translation, content validity, and face validity assessment, followed by discussions with panels of eye care experts. Data for EFA were collected through interviews with subjects aged 50 and older, who had visual acuity worse than 6/18 due to cataracts or had undergone cataract surgery. Responses were analyzed for factor loadings and reliability. Principal Axis Factoring (PAF) was used for factor extraction, initially based on Eigenvalues > 1, and later fixed at eight factors. Factors were rotated using Varimax with Kaiser Normalization. Items with weak factor loadings were removed iteratively, with re-analysis conducted after each removal.   Results A total of 287 subjects were recruited and consented to EFA. All 40 items in the questionnaire (knowledge, attitude, perception and practice) were combined and analysed. The Kaiser-Meyer-Olkin (KMO) test was 0.714, indicating that factor analysis was suitable for exploring the underlying structure. Bartlett's test of Sphericity was highly significant (p < 0.001), indicating that the variables (questions) were sufficiently interrelated for factor analysis. Factors 3 and 7 had only two questions, although they showed fairly good loading with satisfactory correlation. The Cronbach's alpha reliability of all the factors varies from 0.50 to 0.72 (total = 0.72). The final questionnaire consisted of six factors and 22 questions.   Conclusions The developed and validated questionnaire demonstrated an acceptable factor structure related to knowledge, attitude, perception, and practice in evaluating cataract surgery uptake. This tool provides a reliable method for assessing cataract surgery uptake in the community.