Psychometric evaluation of the 12-item Well-being Questionnaire for use with people with macular disease.

This paper reports the evaluation of a generic measure of psychological well-being, the 12-item Well-being Questionnaire (W-BQ12), for use with people who have the chronic eye condition, macular disease (MD). The W-BQ12 was incorporated in a self-administered questionnaire which was completed by 1421 members of the Macular Disease Society (MD Society). Unforced factor analysis elicited the expected three factors representing constructs of positive well-being, energy and negative well-being. A forced single-factor solution supported use of the whole scale to measure total general well-being. High Cronbach's alpha coefficients demonstrated good internal consistency reliability in the entire scale (alpha = 0.87) and in subscales (alpha > 0.78). The factor structure matched that found in samples of people with diabetes for whom the W-BQ12 was first developed, indicating construct validity. Expected subgroup differences in the MD sample indicated significantly poorer well-being in women than in men and also in participants who were registered blind or partially sighted compared to those who were not registered. The W-BQ12 will be useful in measuring outcomes in rehabilitative and medical interventions and in researching factors affecting adjustment to MD.