Evaluation and validity of the Danish version of the Adult Strabismus Questionnaire AS-20

PURPOSE Assessing health-related quality of life in patients with strabismus is important in evaluating the clinical benefits of strabismus treatment. The purpose of this study was to translate the Adult Strabismus Quality of Life Questionnaire (AS-20) into Danish and evaluate its reliability and validity in adult patients with strabismus in Denmark. METHODS The AS-20 was translated into Danish in accordance with standard international adopted methods. We presented the questionnaire to 64 adults with strabismus and to 13 non-strabismic adult controls. We tested the reliability of the Danish version by reassuring test-retest reliability, estimated the internal consistency, and analyzed the validity (discriminatory power) of the questionnaire by comparing patient scores with scores from control individuals. RESULTS The Danish AS-20 produced high level of internal consistency (Cronbach's α values) for both subscales (psychosocial: 0.95 and functional: 0.85). We found good discriminatory power of the AS-20. The patients scored significantly lower not only on AS-20 composite score (median =63, interquartile range [IQR] =44-79) compared to healthy individuals (median =98, IQR =93-100) (P<0.0001) but also on all individual questions in both subscales (psychosocial: 1-10 and functional: 11-20). CONCLUSION The Danish version of AS-20 shows high reliability and validity, and in our opinion, AS-20 is therefore a suitable instrument for evaluating self-perceived psychosocial and functional influence of strabismus.