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Editors Selection IGR 23-4

Quality of life: Validity of questionnaires

Comment by Anne Coleman on:

19353 Are standard instruments valid for the assessment of quality of life and symptoms in glaucoma?, Lamoureux EL; Ferraro JG; Pallant JF et al., Optometry and Vision Science, 2007; 84: 789-796

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In a case series study design, Lamoureux et al. (826) evaluated the validity of two questionnaires, the Visual Impairment Instrument (IVI) and the Glaucoma Symptom Scale (GSS). Although the investigators did not have a control group, they did enroll 175 subjects, who were recruited from one public and one private vision care practice in Victoria, Australia, had mean age of 71 years, and had mild, moderate, or severe glaucomatous visual field loss in at least one eye according to the Advanced Glaucoma Intervention Study scores. The authors reported that both questionnaires are suboptimal in assessing the effect of glaucoma on quality of life in patients with good central vision. The statistical methods which were used to evaluate both questionnaires are hard to follow and the graphs are difficult to interpret. Although at least 87% of the subjects had visual acuity of 6/9 or better in one eye, the authors did not control the analyses for visual acuity or report on the relationship between visual acuity and IVI and GSS in their study population. The authors' conclusion that both questionnaires performed poorly is surprising because they did report that the Rasch-scaled IVI could discriminate between subjects with mild, moderate, and severe visual field loss which is consistent with the recent reports from the Los Angeles Latino Eye Study (LALES) where there was a linear association between NEI VFQ-25 scores and visual field declines in all subjects¹ and in subjects with glaucoma.² Although the GSS was not associated with visual field loss, the GSS was developed to measure the symptoms of glaucoma patients, not their vision-specific quality of life, so it is unclear whether it should be associated with visual field loss. Because the NEI VFQ 25 is the most commonly used instrument for assessing vision-specific quality of life, and it has performed well in subjects who were unaware of their diagnosis of glaucoma,² a glaucoma-specific instrument to assess quality of life in glaucoma subjects may not need to be developed as the authors recommend.

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