The 6-Item Vision-Related Quality of Life and Limitations Questionnaire: Evaluation of Psychometric Properties.

Abstract

We developed the Vision-related Quality of life and Limitations Questionnaire (VQL-6), a screening instrument to signal a need for additional care resulting from reduced vision-related quality of life in patients with chronic ophthalmic diseases. The aim of the present study was to evaluate psychometric properties. A Dutch population-based sample of 2032 participants (mean age, 55 ± 19 years) completed the VQL-6 and other questionnaires on vision-related quality of life, executive functioning, attention, mental health, and symptom validity. In addition, we recruited a sample of 208 ophthalmic patients (mean age, 72 ± 12 years) and 98 age and gender similar controls (mean age, 69 ± 11 years) who completed the VQL-6 and the National Eye Institute Visual Function Questionnaire-25. We studied the factor structure, internal consistency, convergent and divergent validity, and known-groups validity. For the factor analyses, the population-based sample was split randomly in two subsamples. Exploratory factor analysis on the first subsample suggested a two-factor model (visual limitations and general health and quality of life), which was supported by confirmatory factor analyses on the second subsample, and on the patients. The VQL-6 demonstrated good internal consistency within each factor (0.78-0.89), sufficient convergent (r2= 55%) and divergent validity (r2 = 11%-24%), and good known-groups validity (Cohen's r = 0.57; P < 0.001). The VQL-6 has a robust two-factor structure and seems to be a valid tool to assess vision-related quality of life. Additional validation is needed in patients with chronic ophthalmic diseases. Future research is needed to determine if the VQL-6 can be used to identify patients with chronic ophthalmic diseases who are in need of additional care.