Validation of a Quality of Life Questionnaire in the Pacific Island

Structural validity of the impact of vision impairment questionnaire among patients with visual impairment in Thailand

Background

The Impact of Vision Impairment (IVI) questionnaire is used to assess vision-related quality of life (VRQOL) among patients with visual impairment. This study aims to evaluate the factor structure of the IVI in the context of Thai culture to assess psychometric properties.

Methods

This cross-sectional study was conducted between February and July 2022. Purposive sampling was used to include 502 patients with visual impairment who received treatment at a tertiary eye center, King Chulalongkorn Memorial Hospital, Bangkok, Thailand. The data were collected using the interviewer-administered questionnaire. The participants were randomly divided into two groups: one employed for exploratory factor analysis (EFA; n = 251) and the other for confirmatory factor analysis (CFA; n = 251).

Results

EFA yielded 28 items that supported a four-factor structure: behaviors related to mobility and independence (8 items), reading (3 items), self-dependence (7 items), and emotional impact of vision loss (10 items), with a total variance of 64.9 %. The model fit was good: χ2/df = 1.66, CFI = 0.949, TLI = 0.940, RMSEA = 0.052, and SRMR = 0.041. The AIC and BIC for the bifactor four-factor model (17,484.86 and 17,879.41, respectively) were lower than those for the bifactor three-factor model (17,566.44 and 17,961.29, respectively), indicating that the former showed the best fit.

Conclusions

Given its good reliability and validity, the IVI scale has been extensively used to explore the impact of visual impairment on the VRQOL of patients in the clinical setting, thus greatly benefitting researchers, healthcare providers, and ophthalmologists.

Defining a Minimum Set of Standardized Patient-centered Outcome Measures for Macular Degeneration

PURPOSE

To define a minimum set of outcome measures for tracking, comparing, and improving macular degeneration care.

DESIGN

Recommendations from a working group of international experts in macular degeneration outcomes registry development and patient advocates, facilitated by the International Consortium for Health Outcomes Measurement (ICHOM).

METHODS

Modified Delphi technique, supported by structured teleconferences, followed by online surveys to drive consensus decisions. Potential outcomes were identified through literature review of outcomes collected in existing registries and reported in major clinical trials. Outcomes were refined by the working group and selected based on impact on patients, relationship to good clinical care, and feasibility of measurement in routine clinical practice.

RESULTS

Standardized measurement of the following outcomes is recommended: visual functioning and quality of life (distance visual acuity, mobility and independence, emotional well-being, reading and accessing information); number of treatments; complications of treatment; and disease control. Proposed data collection sources include administrative data, clinical data during routine clinical visits, and patient-reported sources annually. Recording the following clinical characteristics is recommended to enable risk adjustment: age; sex; ethnicity; smoking status; baseline visual acuity in both eyes; type of macular degeneration; presence of geographic atrophy, subretinal fibrosis, or pigment epithelial detachment; previous macular degeneration treatment; ocular comorbidities.

CONCLUSIONS

The recommended minimum outcomes and pragmatic reporting standards should enable standardized, meaningful assessments and comparisons of macular degeneration treatment outcomes. Adoption could accelerate global improvements in standardized data gathering and reporting of patient-centered outcomes. This can facilitate informed decisions by patients and health care providers, plus allow long-term monitoring of aggregate data, ultimately improving understanding of disease progression and treatment responses.

The Impact of Vision Impairment (IVI) Questionnaire; Validation of the Thai-Version and the Implementation on Vision-Related Quality of Life in Thai Rural Community

The objective of this study is to validate the Thai-version of the impact of vision impairment (IVI) questionnaire and to evaluate its impact on vision-related quality of life (VRQoL) in southern Thailand. The IVI questionnaire was translated into Thai according to WHO translation guidelines. In addition to the routine ophthalmological examinations, a Thai version of the IVI questionnaire was administered to all participants. A total of 120 patients with visual impairment who presented at Songklanagarind hospital, Songkhla province, were enrolled in the study; 30 had age-related macular degeneration (AMD), 30 had cataract, 30 had diabetic retinopathy, 30 had glaucoma, and 30 non-visually impaired individuals comprised the control group. Statistical analysis demonstrated the Thai-version IVI questionnaire is valid and reliable to evaluate the VRQoL of the Thai patients through three subscales: (i) mobility and independence, (ii) reading and accessing information, and (iii) emotional well-being. The results demonstrated high consistency in all subscales with Cronbach’s alpha ranging from 0.787 to 0.849. Rasch analysis revealed the validity of the Thai-version IVI to assess VRQoL through all three subscales. Test-retest reliability was also high (intraclass correlation coefficient = 0.96). The composite score of the IVI was significantly higher in participants with visual impairment compared with healthy participants. Moreover, the subscale scores of reading and accessing information, and emotional well-being were highest in participants with AMD. While the subscale scores of mobility and independence were highest among those with either cataracts or diabetic retinopathy. The symptoms of the common vision impairment diseases are associated with an adverse impact on VRQoL in a clinic-based population as demonstrated in this study.

Rasch analysis of Impact of Vision Impairment for Children questionnaire

PURPOSE

To validate the Indian-translated Impact of Vision Impairment for Children (IVI_C), a vision-related quality of life (VRQoL) instrument, and to investigate the effect of sociodemographic and ocular characteristics on VRQoL.

METHODS

The 24-item IVI_C was administered face to face to 221 children with vision impairment (VI) (mean age, 12.6 years; male, 68%) referred to the Vision Rehabilitation Centres. Rasch analysis was used to investigate the IVI_C for key indices such as measurement precision as measured by person separation (minimum recommended value, 2.0), unidimensionality (i.e., whether all the items contribute toward measurement of a single underlying construct as assessed by item fit and principal component analysis of residuals), targeting of items to participants' VRQoL (i.e., matching of item difficulty to participant ability; ideal targeting, <1.0 logits). Univariate analysis was performed to determine if the person scores of IVI_C were significantly different across participant subgroups stratified by sociodemographic and ocular characteristics, including the severity of VI.

RESULTS

The IVI_C showed misfit to the model and lacked unidimensionality. Principal component analysis confirmed the presence of an additional construct, mobility, but it did not possess adequate person separation when assessed individually. Deleting the mobility-related items restored unidimensionality, but additional items misfit, necessitating item reduction. Finally, a 17-item IVI_C possessed good measurement precision (person separation, 2.04), was unidimensional (albeit not purely), and consisted of items that fit the Rasch model and were well targeted to the participants' VRQoL (targeting 0.76 logits). There was no statistically significant difference in the VRQoL across subgroups stratified by age, sex, type of school, cause of VI, duration of vision loss, and severity of VI (p > 0.05 for all).

CONCLUSIONS

The revised 17-item IVI_C is shorter and has better psychometric properties than the original version in school-aged children with VI in India, and the responses are unrelated to sociodemographic and clinical variables. Although it has the potential for use in cross-sectional and outcomes research in children with VI, caution should be exercised while interpreting the 17-item IVI_C scores given the presence of slight multidimensionality.