Danish version of Visual Function Questionnaire-25 and its use in age-related macular degeneration.

Introduction: Assessment of visual function can be a complex task and objective means of measurement of visual function do not always correlate with patients' self-perceived visual abilities. The purpose of this study was to translate the visual function questionnaire (VFQ)-25 into Danish with particular focus on its use in patients with late age-related macular degeneration (AMD).

Material and methods: The translation was done in accordance with standard internationally adopted methods. This includes forward translation, back translation, examination of translation quality, and adjudication by bilingual speakers. We presented the questionnaire to 120 consecutive patients with exudative AMD referred to our department and to 25 healthy individuals. We tested the reliability of the Danish version by measuring test-retest reliability, estimated the internal consistency of the questionnaire (Cronbach's α-value) and analysed the discriminatory power (validity) of the questionnaire by comparing scores of patients with scores from control individuals without known eye disease.

Results: The translated questionnaire produced high test-retest correlations (range 0.8-0.9), had a relatively high-level of internal consistency (range 0.4-0.9) and a high discriminatory power.

Conclusion: The Danish version of VFQ-25 produces acceptable values of validity and reliability in patients with AMD.