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Assessment of vision-related function in patients with age-related macular degeneration
Paul J Mackenzie1, Tom S Chang, Ingrid U Scott
1Division of Vitreo-Retinal Surgery, Department of Ophthalmology, University of British Columbia, Vancouver, BC, Canada.
Objective:
To investigate the validity of the visual function index (VF-14) in assessing visual function in patients with age-related macular degeneration (AMD).
Design:
Prospective noncomparative observational case series.
Participants:
One hundred fifty-nine consecutive patients attending a sole practitioner's academic retina-only clinic from May 1998 through August 1998 and from May 1999 through August 1999.
Main Outcome Measures:
Correlations were calculated between the VF-14 scores and the medical outcomes study 36-item short form (SF-36), weighted comorbidity scale, visual acuity and clinical AMD severity (stage), and vision self-assessment scales. Documentation of the severity of macular degeneration was performed by a sole examiner.
Results:
There was a moderately strong correlation between visual acuity and trouble with vision (r = 0.51), satisfaction with vision (r = -0.50), and overall quality of vision (r = -0.56). A strong correlation was noted between VF-14 score and patients' self-rating of amount of trouble with vision (r = -0.67), satisfaction with vision (r = 0.62), and overall quality of vision (r = 0.67). In comparison, correlations between SF-36 score and patients' self-rating of amount of trouble with vision, satisfaction with vision, and overall quality of vision ranged from r = 0.37 to r = -0.40. Linear regression analysis for the overall study population indicated that AMD severity was not an independently significant predictor of VF-14 score after adjusting for visual acuity. However, among patients with 20/20 vision in the better eye, AMD severity was an independently significant predictor of VF-14 score after adjusting for visual acuity in the worse eye.
Conclusions:
The VF-14 exhibits a considerable degree of validity as a measure of functional impairment in patients with AMD. Age-related macular degeneration severity was an independently significant predictor of VF-14 score in the group of patients with 20/20 vision in the better eye, but this did not hold true for the overall study population. Age-related macular degeneration is associated with substantial impairment in reported visual function.