Vision and quality of life: development of methods for the VisQoL vision-related utility instrument.
OBJECTIVE
To describe the methods and innovations used in constructing the VisQoL, a vision-related utility instrument for the health economic evaluation of eye care and rehabilitation programs.


METHODS
The VisQoL disaggregates vision into six items. Utilities were estimated for item worst responses (the worst level for each item, with all other items at their best level) and VisQoL all-worst responses (all items at their worst level) using the time trade-off procedure. Time trade-off questions require people to imagine living a fixed number of years with a particular health condition and then indicate how many of those years of life they would be willing to trade to have perfect health. Where respondents indicated a health state was "worse than death" negative utilities were estimated. Time trade-off questions minimized the "focusing effect," which occurs if respondents discount the fact that all other aspects of health are at their best when answering questions, by using pictorial and verbal aids.


RESULTS
Item utilities were combined using a multiplicative model, and VisQoL model utilities placed on a scale where 0.00 and 1.00 represent full health and death, respectively. The VisQoL allows utilities to be calculated for a wide range of vision-related conditions.


CONCLUSIONS
The 6-item VisQoL has excellent psychometric properties and is specifically designed to be sensitive to vision-related quality of life. It is the first instrument to permit the rapid estimation of utility values for use in economic evaluations of vision-related programs.
Peacock
Stuart
S
Centre for Health Economics in Cancer, British Columbia Cancer Agency, Vancouver, British Columbia, Canada. speacock@bccrc.ca
Misajon
Roseanne
R
Iezzi
Angelo
A
Richardson
Jeff
J
Hawthorne
Graeme
G
Keeffe
Jill
J
D003362:Cost-Benefit Analysis; D006801:Humans; D008962:Models, Theoretical; D011594:Psychometrics / Q000379:methods; D011788:Quality of Life; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D014786:Vision Disorders / Q000523:psychology*; D014785:Vision, Ocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology; D019987:Persons with Visual Disabilities / Q000523:psychology*
Qual Life Res. 1999 May;8(3):209-24
10472152
Qual Life Res. 2000;9(10):1127-35
11401045
Trans Am Ophthalmol Soc. 2000;98:91-6; discussion 96-9
11190044
Aust N Z J Public Health. 2002 Apr;26(2):116-9
12054328
Med Decis Making. 2001 May-Jun;21(3):190-9
11386626
J Health Econ. 1986 Mar;5(1):1-30
10311607
Arch Ophthalmol. 2002 Aug;120(8):1041-4
12149057
Invest Ophthalmol Vis Sci. 2005 Nov;46(11):4007-15
16249474
J Clin Epidemiol. 1998 Nov;51(11):1115-28
9817129
Invest Ophthalmol Vis Sci. 1997 Jan;38(1):72-82
9008632
Psychol Bull. 1955 Jul;52(4):281-302
13245896
Aust N Z J Public Health. 1999 Apr;23(2):147-53
10330728
Med Care. 1995 Apr;33(4 Suppl):AS236-44
7723452
Soc Sci Med. 1994 Jul;39(1):7-21
8066489
Ann Med. 2001 Jul;33(5):375-84
11491197
Invest Ophthalmol Vis Sci. 2002 Apr;43(4):927-35
11923230
Health Policy. 1990 Dec;16(3):199-208
10109801
Med J Aust. 2001 Mar 19;174(6):271-5
11297113
Med Care. 2002 Feb;40(2):113-28
11802084