Psychometric properties of the Croatian version of the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25).

ABSTRACT

PURPOSE: The purpose of the study was to translate, adapt and validate the Croatian version of the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25) in participants with visual impairment. This study also aims at evaluating the relationship between visual impairment and health-related quality of life (HRQoL). METHODS: The prospective observational study was conducted at the University Hospital Centre Zagreb, Department of Ophthalmology. The sample consisted of 175 patients with four chronic ocular diseases cataract, glaucoma, diabetic retinopathy and age-related macular degeneration. The translation of the NEI VFQ-25 to Croatian was conducted following the standardised procedure. All participants underwent an ophthalmological examination and completed the NEI VFQ-25 and the Medical Outcomes Study Short Form-36 Questionnaire (SF-36). In order to assess the psychometric properties of the NEI VFQ-25, we calculated Cronbach's α coefficient, intraclass correlation coefficient (ICC), convergent and discriminant validity, as well as criterion and concurrent validity. RESULTS: Results show high internal consistency (Cronbach α range 0.739-0.932) and high test-retest reliability (ICC 0.876-0.975) for all subscales. None of the items had failed either convergent or discriminant validity. Moderate to high Spearman's rho coefficients of correlations were found between best corrected visual acuity and eight subscales in the NEI VFQ-25 (0.430 < ρ < 0.631). Moderate correlations were found between comparable domains in the NEI VFQ-25 and in the SF-36 questionnaire (p < 0.01). CONCLUSION: The Croatian version of the NEI VFQ-25 has very good psychometric properties and can be a useful instrument for assessing vision-related quality of life in Croatian population with chronic ophthalmic diseases.