Abstract
Purpose: :
This study investigates the relationships between vision and health in terms of previously validated health utility measures. Additionally, it compares patient-based and community-based evaluations of health state. It evaluates the role that comorbidities play in how low vision patients rate their quality of life. Understanding the relationship between health-related quality of life (HRQoL) and vision-related quality of life (VRQoL) will more accurately define the true utility of ophthalmologic and rehabilitative intervention.
Methods: :
Telephone interviews of Wilmer low vision patients were conducted over 2 phone calls, separated by a minimum of one week. One phone call included vision-related surveys; the other included health-related surveys. The surveys used were the Time Trade Off (TTO) and Standard Gamble (SG) as they relate to both vision and health and the Euro-QoL 5D (EQ-5D). Chart review was completed to identify comorbidities, visual acuity, visual fields, contrast sensitivity and ocular diagnoses.
Results: :
Utilities were measured in 38 low vision patients. The EQ-5DI is essentially constant for all patients surveyed with a mean of .77 and minimal variance from the mean (SD=0.12). In contrast, both the SG and TTO health utilities showed a broad distribution of responses. The EQ-5DI did not correlate with either the SG (r=0.16, p=0.17) or TTO (r=0.17, p=0.16). SG and TTO are moderately correlated with a bivariate regression line not significantly different from the identity line for both health (r=.66, m=.96, b=0.1) and vision (r=.45, m=1.15, b=-0.05). There are strong correlations when comparing SG vision to SG health (r= .77, m=.86, b=.18) and TTO vision to TTO health (r= .70, m=.72, b=.28).
Conclusions: :
The data support the hypothesis that SG and TTO measure the same utility construct, both for vision and for overall health in low vision patients, but reliability of the estimates is weak. The results agree with previous studies that compared vision-specific and health utilities, in that health utilities are less than or equal to vision utilities. Utilities estimated from EQ-5D response show minimal variation in the low vision patient sample and, more important to the interpretation of these indices, do not correlate with either the TTO or SG health utility for low vision patients.
Keywords: quality of life • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • low vision