Comparison between the English and Bahasa Malaysia language versions of the Visual Functioning Questionnaire (VFQ-25) for use in patients with cataracts

BACKGROUND: We conducted the study to compare the psychometric properties of the English version of the Questionnaire and the Bahasa Malaysia (Malay Language) version regarding the vision-related Quality of Life of patients with cataracts.

METHODS: The Malay version was translated by two independent translators who were well versed in both languages. We carried out a cross-sectional study collecting data between June 2017 and March 2018 in the pre-operative Eye Clinic of Hospital Melaka with 224 respondents (mean age 66.8 years) and another 204 respondents (mean age 64.3 years) participating in the English version and Malay version of the Questionnaire respectively. Methods used to validate the standard questionnaire included the use of construct validity via factor analysis and the deployment of reliability test through assessment of internal consistency via Cronbach's alpha.

RESULTS: We observed both English and Bahasa Malaysia versions to have high reliability with Cronbach's alpha values of 0.90 and above in factors on difficulty with activities and responses to vision problems. Exploratory factor analysis performed revealed that the three-factor model fits the data well for the English version of the questionnaire - difficulty with activities (23.81 % of variance), responses to vision problem (22.22 % of variance) and general health and vision (14.68 % of variance). The Bahasa Malaysia version of the questionnaire produced three factors with two of the factors resembling the factors from the original version of the questionnaire - difficulty with activities (24.3 % of variance) and responses to vision problem (23.7 % of variance). Item response theory analysis revealed that these factors for both English and Bahasa Malaysia versions comprised of adequately fitted items.

CONCLUSION: The present study observed that both the English and Bahasa Malaysia versions of the NEI VFQ-25 have comparable construct validity to the original American version. With high validity and reliability, the tool shall be able to provide health care providers the assessment of impact due to cataract and other ophthalmic conditions on the vision-related quality of life of ophthalmic patients.