Structural validity of the impact of vision impairment questionnaire among patients with visual impairment in Thailand.

BACKGROUND

The Impact of Vision Impairment (IVI) questionnaire is used to assess vision-related quality of life (VRQOL) among patients with visual impairment. This study aims to evaluate the factor structure of the IVI in the context of Thai culture to assess psychometric properties.

METHODS

This cross-sectional study was conducted between February and July 2022. Purposive sampling was used to include 502 patients with visual impairment who received treatment at a tertiary eye center, King Chulalongkorn Memorial Hospital, Bangkok, Thailand. The data were collected using the interviewer-administered questionnaire. The participants were randomly divided into two groups: one employed for exploratory factor analysis (EFA; n = 251) and the other for confirmatory factor analysis (CFA; n = 251).

RESULTS

EFA yielded 28 items that supported a four-factor structure: behaviors related to mobility and independence (8 items), reading (3 items), self-dependence (7 items), and emotional impact of vision loss (10 items), with a total variance of 64.9 %. The model fit was good: χ2/df = 1.66, CFI = 0.949, TLI = 0.940, RMSEA = 0.052, and SRMR = 0.041. The AIC and BIC for the bifactor four-factor model (17,484.86 and 17,879.41, respectively) were lower than those for the bifactor three-factor model (17,566.44 and 17,961.29, respectively), indicating that the former showed the best fit.

CONCLUSIONS

Given its good reliability and validity, the IVI scale has been extensively used to explore the impact of visual impairment on the VRQOL of patients in the clinical setting, thus greatly benefitting researchers, healthcare providers, and ophthalmologists.