Psychometric evaluation of the MacDQoL individualized measure of the impact of macular degeneration on quality of life.

Mitchell, J, Wolffsohn, JS, Woodcock, Alison, Anderson, SJ, McMillan, CV, ffytche, T, Rubinstein, M, Amoaku, W and Bradley, Clare

(2005)

Mitchell, J, Wolffsohn, JS, Woodcock, Alison, Anderson, SJ, McMillan, CV, ffytche, T, Rubinstein, M, Amoaku, W and Bradley, Clare (2005) Psychometric evaluation of the MacDQoL individualized measure of the impact of macular degeneration on quality of life.. Health and Quality of Life Outcomes, 3 (25).

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Abstract

Background: The MacDQoL is an individualized measure of the impact of macular degeneration (MD) on quality of life (QoL). there is preliminary evidence of its psychometric properties with sensitivity to severity of MD. The aim of this study was to carry out further psychometric evaluation with a larger sample and investigate the measure's sensitivity to MD severity.

Methods: Patients with MD (n= 156.99 women, 57 men, mean age 79 + 13 years), recruited from eye clinics (one NHS, one private) completed the MacDQoL by telephone interview and later underwent a clinic vision assessment including near and distance visual acuity (VA), comfortable near VA contrast sensitivity, colour recognition, recovery from glare and presence of absence of distortion or scotoma in the central 10 degrees of the visual field.

Results: The completion rate for the MacDQoL items was 99.8%. Of the 26 items, three were dropped from the measure due to redundancy. A fourth was retained in the questionnaire but excluded when computing the scale score. Principal components analysis and Cronbach's alpha (0.944) supported combining the remaining 22 items in a single scale. Lower MacDQoL scores, indicating more negative impact of MD on QoL, were associated with poorer distance VA (better eye r = -0.431 p < 0.0001; worse eye r = -0.350 p < 0.001; binocular vision r = -0.419 p < 0.001). Poorer MacDQoL scores were associated with poorer contrast sensitivity (better eye = 0.392 p < 0.0001 ; binocular vision r = 0.423 p < 0.001), poorer colour recognition (r = 0.417 p < 0.001) and poorer comfortable near VA (r = -0.283, p < 0.001). The MacDQoL differentiated between those with and without binocular scotoma (U = 1244 p < 0.001).

Conclusion: The MaDQoL 22-item scale has excellent internal consistency reliability and a single-factor structure. The measure is acceptable to respondents and the generic QoL item, MD-specific QoL item and average weighted impact score are related to several measures of vision. The MacDQoL demonstrates that MD has considerable negative impact on many aspects of QoL, particularly independence, leisure activities, dealing with personal affairs and mobility. The measure may be valuable for use in clinical trials and routine clinical care.

Information about this Version

This is a Submitted version
This version's date is: 14/4/2005
This item is not peer reviewed

Link to this Version

https://repository.royalholloway.ac.uk/items/ecce8401-b152-4448-5d89-0500c38c5d3d/8/

Item TypeJournal Article
TitlePsychometric evaluation of the MacDQoL individualized measure of the impact of macular degeneration on quality of life.
AuthorsMitchell, J
Wolffsohn, JS
Woodcock, Alison
Anderson, SJ
McMillan, CV
ffytche, T
Rubinstein, M
Amoaku, W
Bradley, Clare
Uncontrolled KeywordsMacular degeneration, MacDQoL, Quality of Life
DepartmentsFaculty of Science\Psychology

Identifiers

doihttp://dx.doi.org/10.1186/1477-7525-3-25

Deposited by Research Information System (atira) on 18-Nov-2014 in Royal Holloway Research Online.Last modified on 18-Nov-2014


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