Utilities for quality of life from time trade–off and conjoint analysis in age related macular degeneration

Abstract

Abstract: : Purpose: To determine utilities and the relative importance of different daily tasks affecting vision related quality of life (QoL) in patients with age related macular degeneration (AMD). Methods:Several tests were given to 120 patients attending an AMD clinic including visual function measures, the NEI–VFQ25 QoL questionnaire, an impact of disease questionnaire (IoD), a conjoint analysis task (CA) to assess patient values and relative importance of daily tasks, and time trade–off (TTO) utility judgements determined as a proportion (P) of the respondent's estimate of their remaining expected life years. AMD was categorised into a binocular status of 'mild', 'moderate' and 'severe' based on the international classification and grading system. Results:Patients mean age = 77.8 yrs (SD 6.7), mean binocular best corrected distance logMAR acuity = 0.50 (SD 0.42), mean binocular near acuity = 0.69 (SD 0.43), and mean contrast sensitivity (Pelli–Robson) = 1.19 (SD 0.35). Using binocular AMD status 15% of patients were classified as ‘mild’, 32% as ‘moderate’ and 53% as ‘severe’. Principal component analysis of the CA utilities showed relative independence of the attributes used in the conjoint task but there was a complex factor structure relating to the levels of difficulty associated with each attribute. TTO utilities (1–P) for remaining life were 0.96 for 'mild', 0.92 for 'moderate' and 0.71 for 'severe' AMD. CA showed that problems of greatest importance were outdoor mobility and reading ability, while the ability to recognise faces and problems from glare were rated as least important. QoL and IoD questionnaires showed that all stages of the disease had a significant impact on emotional factors but the most significant effects on the ability to perform daily tasks occurred between the ‘moderate’ to ‘severe’ forms of the disease. Conclusions: CA suggested preference for preserving an independent life–style, while QoL questionnaires showed that, except for emotional factors, the most significant effects on daily activities occurred between ‘moderate’ and ‘severe’ AMD. Utilities, expressed in terms of estimated remaining life years from TTO, also showed that the greatest change occurred between 'moderate' to 'severe' AMD. Commercial relationship: The research was supported by Allergan Limited.

Keywords: age–related macular degeneration • quality of life