Design of an individualised measure of the impact of macular disease on quality of life (the MacDQoL)

Abstract

The aim of this study was to design an individualised questionnaire to measure the impact of macular disease (MD) on quality of life (QoL). Principles underlying the Schedule for the Evaluation of Individual Quality of Life (SEIQoL) interview method and the Audit of Diabetes-Dependent Quality of Life (ADDQoL) diabetes-specific questionnaire influenced the Macular Disease-Dependent Quality of Life (MacDQoL) design. The MacDQoL specifies domains of QoL that were selected using focus group methodology and refined following a postal pilot study of members of the UK Macular Disease Society (MDS). Respondents rated the impact of MD on each domain and the importance of each domain to their QoL. Mean domain scores from 69 respondents indicated that MD had a negative impact on all the domains of QoL investigated in the measure. There was preliminary evidence of good internal consistency reliability (Cronbach's alpha = 0.93, n = 37). Respondents who were registered partially sighted (P/S) or blind reported poorer QoL than those who were not registered (Kruskal-Wallis: chi2 = 14.03, n = 62, p < 0.001). This evidence suggests that the measure will be sensitive to subgroup differences. The instrument has been further refined following the pilot study. The MacDQoL is being used in clinical trials and psychometric evaluation of the measure will be carried out using trial data. The measure is available for clinical use and has been linguistically validated in 15 other languages.