Title:
Assessing disutility associated with diabetic retinopathy, diabetic macular oedema and associated visual impairment using the Vision and Quality of Life Index.

Abstract:
Use of generic multi-attribute utility instruments (MAUI) to assess the impact of diabetic retinopathy (DR) on health-related quality of life (HRQoL) has produced inconsistent findings. Therefore, we assessed the impact of DR, diabetic macular oedema (DME) and associated visual impairment on vision-related QoL (VRQoL) using a vision-specific MAUI.
In this cross-sectional study, 203 diabetic patients were recruited from specialised eye clinics in a Melbourne tertiary eye hospital. Severity of combined DR/DME was categorised as: no DR/no DME, mild non-proliferative DR (NPDR) and/or mild DME; moderate NPDR and/or moderate DME and vision-threatening DR (severe NPDR or proliferative DR (PDR) and/or severe DME) in the worse eye. Visual impairment was categorised as: none (up to 0.18 logMAR); mild (from 0.18 to 0.3 logMAR); moderate (from 0.3 to 0.48 logMAR); severe (from 0.48 to 0.78 logMAR); and profound (worse than 0.78 logMAR). The Vision and Quality of Life Index (VisQoL) vision-specific MAUI was the main outcome measure. As the distribution of the utilities was skewed, independent associations with covariates were explored using multivariable quantile regression models (five groups: 15(th) , 30(th) , 45(th) , 60(th) and 75(th) percentiles) ranging from poorest to highest VRQoL.
Participants' median age was 65 years (range: 27 to 90 years). Of the 203 participants, 50 (24.6 per cent) had no DR/DME, 24 (11.8 per cent) had mild NPDR/DME, 47 (23.2 per cent) had moderate NPDR/DME and 82 (40.4 per cent) had vision-threatening DR. After adjusting for relevant covariables, only profound visual impairment was independently associated with VisQoL utilities (β= -0.297 ± 0.098 p < 0.01). Severity of DR/DME was not significantly associated with any group of VisQoL utilities.
The variation in VisQoL utilities was attributed to profound visual impairment but not mild, moderate or severe visual impairment or DR/DME severity. These findings support the use of vision-specific MAUI to capture the impact of profound visual impairment associated with DR and DME. A DR-specific MAUI might be required to assess the specific utility deficits associated with DR/DME across the spectrum of the condition.