Are Standard Instruments Valid for the Assessment of Quality of Life and Symptoms in Glaucoma?

Evaluation of the test-retest and inter-mode comparability of the Impact of Vision Impairment questionnaire in people with chronic eye diseases

PURPOSE

The main objective of this study is to assess the test-retest and inter-administration mode reliability of the Impact of Vision Impairment profile (IVI), a common patient-reported outcome measure (PROM) for people with chronic eye diseases.

METHODS

The IVI was administered to adult patients with stable, chronic eye diseases two to four times per participant (average intervals between administrations 12 to 20 days; maximum two phone interviews, paper administration, electronic administration) by two trained interviewers. Rasch models were fit to the data. Intra-class correlation coefficients (ICCs), mean differences and Cronbach's alpha between test-retest administrations (two phone interviews) and inter-mode comparisons were calculated.

RESULTS

Two hundred-sixteen patients (mean age 67 ± 12 years, 40% male) were included in the study. The IVI met all psychometric requirements of the Rasch model, and the division into the domains of functional items (IVI_F) and emotional items (IVI_E) corresponded to the German validation study. ICCs (all for IVI_F and IVI_E, respectively) for the retest administrations were 0.938 and 0.912, and 0.853 and 0.893 for inter-mode comparisons phone/paper, 0.939 and 0.930 for phone/electronic, and 0.937 and 0.920 for paper/electronic (all p < 0.01). Mean differences (all for IVI_F and IVI_E, respectively) for the retest administrations were 2.8% and 0.7% and ranged from 2.0% to 6.2% and from 0.4 % to 4.9% between administration modes. Cronbach's alpha ranged from 0.886 to 0.944 for retest and inter-mode comparisons.

CONCLUSION

Due to the high test-retest reliability and the almost equally high comparability of different modes of administration of the IVI, the study endorses its use as a robust PROM to capture vision-related quality of life. Our results further support the use of the IVI as an endpoint in clinical trials and may simplify implementing it in both clinical trials or real-world evidence generation by offering multiple administration modes with high reliability.

Evaluating Measurement Properties of Patient-Reported Outcome Measures in Glaucoma: A Systematic Review

TOPIC

The purpose of the current study was to systematically identify and evaluate existing patient-reported outcome measures (PROMs) for clinical glaucoma practice.

CLINICAL RELEVANCE

Understanding and incorporating patient preferences into decision-making is now recognized as critical for optimal resource allocation, especially in technologically advancing areas, such as minimally invasive surgeries. Patient-reported outcome measures are instruments designed to evaluate the health outcomes that are most important to patients. Despite their recognized importance, especially in the era of patient-centered care, their routine use in clinical settings remains low.

METHODS

A systematic literature search was conducted in 6 databases (EMBASE, MEDLINE, PsycINFO, Scopus, BIOSIS, and Web of Science) from the date of inception. Studies were included in the qualitative review if they reported measurement properties of PROMs in adult patients with glaucoma. COnsensus-based Standards for the selection of health Measurement INstruments guidelines were used to assess the included PROMs. The study protocol is registered with PROSPERO (registration number: CRD42020176064).

RESULTS

The literature search yielded 2661 records. After deduplication, 1259 studies entered level 1 screening, and based on title and abstract review, 164 records proceeded to full-text screening. In 48 included studies, 70 instrument reports discuss 43 distinct instruments in 3 major categories: glaucoma-specific, vision-specific, and general health-related quality of life. Most used measures were glaucoma-specific (Glaucoma Quality of Life [GQL] and Glaucoma Symptom Scale [GSS]) and vision-specific (National Eye Institute Visual Function Questionnaire [NEI VFQ-25]). All 3 have sufficient validity (especially construct), with GQL and GSS having sufficient internal consistency, cross-cultural validity, and reliability, with reports suggesting high methodological quality.

CONCLUSION

The GQL, GSS, and NEI VFQ-25 are the 3 most used questionnaires in a research setting, having considerable validation in a patient population with glaucoma. Limited reports on interpretability, responsiveness, and feasibility in all 43 identified instruments make identifying a single optimal questionnaire for clinical use challenging and highlight the need for further studies.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Different impact of early and late stages irreversible eye diseases on vision-specific quality of life domains

To determine the differential impact of the irreversible eye diseases on vision-related quality of life (VRQoL) in a multi-ethnic Asian population. 2652 participants from the Singapore Epidemiology of Eye Disease Study, with any of the following early and late-stage eye conditions including age-related macular degeneration (AMD, n = 158), diabetic retinopathy (DR, n = 105; non vision threatening [non-VTDR]; VTDR), glaucoma (n = 57) and myopic macular degeneration (MMD, n = 106), or none of the above (controls, 2226 [83.9%]) were included. Rasch-scaled scores of the Emotional well-being Mobility and Reading subscales of the Impact of Vision Impairment (IVI) questionnaire, collectively referred to as "VRQoL" were assessed. Multivariable linear regression analyses and pairwise comparisons adjusting for age, gender, ethnicity, socio-economic status, BMI, smoking, alcohol use, presence of systemic diseases and presenting VI were performed to assess and compare the impact of the presence and severity of each eye condition on the three IVI domains. Multivariable adjusted pairwise comparisons of VRQoL between early stages of the four eye diseases showed no significant differences (all P > 0.05). For late stage diseases, individuals with VTDR had significantly larger decrements in Emotional well-being compared to glaucoma (β - 0.81; 95% CI - 1.47 to - 0.16) and MMD (β - 1.17; 95% CI - 2.16 to - 0.18); and Reading decrements compared to glaucoma (β - 0.66; 95% CI - 1.22 to - 0.11). When compared to late glaucoma, individuals with late AMD (β - 0.76; 95% CI - 1.50 to - 0.01) had significantly larger IVI Mobility subscale decrements. VTDR and late AMD, appear to have the greatest impact on VRQoL, compared to late glaucoma and MMD, suggesting a differential impact of late-stage eye disease categorization on VRQoL.

Glaucoma Symptom Scale: Psychometric properties of the Serbian version

Purpose

The study aim was to translate and validate the Glaucoma Symptom Scale (GSS) in Serbian language.

Methods

Clinical parameters and socio-demographic data were collected for each of the 177 enrolled glaucoma patients. Each eye was classified according to the Glaucoma staging system by Mills into 6 stages. Patients filled out the GSS and National Eye Institute Visual Function Questionnaire (NEI-VFQ 25). The GSS comprises 10 complaints common for glaucoma patients on a topical treatment, grouped into two subscales: SYMP-6 (non-visual) and FUNC-4 (visual problems). The GSS was translated following the customary methodology and its psychometric properties were assessed by using both Classical Test Theory (CTT) and Rasch analysis.

Results

The internal consistency of the Serbian GSS for the whole scale was very good (Cronbach’s alpha = 0.81). On factor analysis items were clustered into 2 factors (48.92% of variance) which corresponded to the original scale. The total and subscale GSS scores correlated significantly with measures of disease severity and also with total score and analogous NEI-VFQ 25 subscale scores. In Rasch analysis we obtained adequate item reliability index (0.90). Almost all items had infit and outfit mean squares in the accepted range. However, measurement precision was poor (low person separation reliability) and targeting revealed a ceiling effect.

Conclusion

When analyzed with CTT the Serbian version of the GSS seems to be a valid instrument, but Rasch analysis revealed some serious measurement flaws, therefore it should not be used in its current format. Further studies to modify and improve GSS are needed prior to its application for Serbian glaucoma patients.

Outcomes After Comprehensive Vision Rehabilitation Using Vision-related Quality of Life Questionnaires: Impact of Vision Impairment and National Eye Institute Visual Functioning Questionnaire

SIGNIFICANCE

This research is significant because, although vision-related quality of life (VRQoL) is improved after vision rehabilitation (VR), patients with certain characteristics respond less positively on VRQoL measures, and this should inform future care.

PURPOSE

The purposes of this study were to evaluate how two VRQoL questionnaires compare in measuring change in patient-reported outcomes after VR and to determine if patient characteristics or occupational therapy (OT) predict higher scores after rehabilitation.

METHODS

In a prospective clinical cohort study, 109 patients with low vision completed the Impact of Vision Impairment (IVI) and the National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25) before and after VR. Comprehensive VR included consultation with an ophthalmologist and OT if required. The relationships of six baseline characteristics (age, sex, visual acuity, contrast sensitivity, field loss, diagnosis) and OT were assessed with VRQoL scores using multivariable logistic regression.

RESULTS

The mean (SD) age was 68.5 (19.2) years, and 61 (56%) were female. After rehabilitation, increases in scores were observed in all IVI subscales (reading [P < .001], mobility [P = .002], well-being [P = .0003]) and all NEI VFQ-25 subscales (functional [P = .01], socioemotional [P = .003]). Those who were referred to OT but did not attend and those who had hemianopia/field loss were less likely to have higher VRQoL in IVI mobility and well-being. Those attending OT for more than 3 hours were less likely to have better scores in emotional NEI VFQ. Men were less likely to have increased scores in functional and emotional NEI VFQ, whereas those with diagnoses of nonmacular diseases had higher odds of having increased scores on the emotional NEI VFQ (all, P < .05).

CONCLUSION

Both the IVI and the NEI VFQ-25 detected change in patients' VRQoL after rehabilitation. Most of the patient characteristics we considered predicted a lower likelihood of increased scores in VRQoL.

Correlation of central field index (10-2 visual field analysis) and activity limitation with increasing severity of glaucoma using glaucoma activity limitation-9 questionnaire

Purpose

The purpose of the study was to analyze the correlation between central field index (CFI) and activity limitation in glaucoma using glaucoma activity limitation-9 (GAL-9) questionnaire.

Methods

This hospital-based, cross-sectional, noninterventional study, included 50 patients diagnosed with glaucoma, with field defect encroaching onto central 10° in Humphrey field analysis 30-2 program, in at least one eye. These patients underwent central 10-2 field analysis and CFI was calculated with the help of a calculator created by us. Patients with severe cognitive impairment were excluded and the rest completed the GAL-9 questionnaire. The data was analyzed to determine the correlation between the CFI and the GAL-9 scores.

Results

There was a moderate correlation between CFI of better eye (r = -0.431, confidence interval "CI" -0.619 to -0.173, P < 0.002) and worse eye (r = -0.342, CI: -0.575 to - 0.058, P < 0.015) with GAL-9, the better eye showing a stronger correlation. Mean deviations (MD) of both better (r = -0.345, CI: -0.556 to -0.069, P < 0.014) and worse eye (r = -0.346, CI: -0.578 to -0.063 P < 0.014) showed similar moderate correlation. Vision of better eye (r = -0.398, CI: -0.577 to -0.210, P < 0.004) showed a stronger correlation with GAL-9 score than worse eye (r = -0.188, CI: -0.475 to 0.100, P < 0.192). Subscales of GAL-9 questionnaire also correlated with better eye status. "Finding dropped objects" had the strongest correlation to CFI of better eye (r = -0.676) and "adjusting to dim lights" had the weakest correlation (r = -0.052).

Conclusion

The better eye status in glaucoma patients correlated better than worse eye with regard to activity limitation, signifying that the better eye has a greater influence on the quality of life and how patients perceive their disability. Furthermore, CFI showed a better correlation with GAL-9 score than MD.

Is normal-tension glaucoma a risk factor for stroke?-A 10-year follow-up study

OBJECTIVES

To investigate whether patients with normal-tension glaucoma (NTG) have a higher incidence of stroke.

DESIGN

A population-based retrospective cohort study based on data from the Taiwan National Health Insurance Research Database (NHIRD) from January 1, 2001, to December 31, 2010.

METHODS

Data were retrospectively collected from the NHIRD. A total of 245 (20.1%) patients with a history of stroke at the time of glaucoma diagnosis were excluded, and 1,218 patients with NTG who were 20 years of age and older were identified. Patients' age, gender and pre-existing comorbidities, including hypertension, diabetes, congestive heart failure, ischemic heart disease, atrial fibrillation and disorders of lipid metabolism, were recorded. The propensity score method with a 1:5 matching ratio was used to minimize selection bias. Cox regression with robust variance estimation was used to estimate the hazard ratio (HR) of developing stroke between the NTG and control groups.

RESULTS

After adjusting for patient age, gender, and pre-existing comorbidities, the HR was 6.34, indicating that the incidence of stroke was significantly higher in patients with NTG than in controls. Furthermore, a higher risk of stroke was also found in most subgroups with the above-mentioned comorbidities.

CONCLUSION

NTG is a significant risk factor for subsequent stroke in most of the described comorbidity subgroups. Early interventions for stroke prevention should be provided to newly diagnosed patients with NTG.

Patient reported outcome measures for visual impairment after stroke: a systematic review

Purpose

The aim of this review was to identify patient reported outcome measures (PROMs) for use in research and clinical practice involving individuals with visual impairment following stroke and to evaluate their content validity against quality assessment criteria.

Method

A systematic review of the literature was conducted to identify articles related to the development and/or validation of PROMS. We searched scholarly online resources and hand searched journals. Search terms included MESH terms and alternatives relating to PROMs, visual impairments and quality of life. Data were extracted relating to the development and validation of the included instruments. The quality of the development process was assessed using a modified version of a PROM quality assessment tool.

Results

A total of 142 PROMs were identified, 34 vision-specific PROMs were relevant and available to be analysed in this review. Quality appraisal identified four highly rated instruments: the National Eye Institute Visual Functional Questionnaire (NEI-VFQ), Activity Inventory (AI), Daily Living Tasks Dependant on Vision (DLTV) and Veterans Affairs Low Visual Function Questionnaire (VA LV VFQ). The four instruments have only been used with either a limited number of stroke survivors or a sub-population within visual impairment following stroke.

Conclusion

No instruments were identified which specifically targeted individuals with visual impairment following stroke. Further research is required to identify the items which a population of stroke survivors with visual impairment consider to be of most importance. The validation of a combination of instruments or a new instrument for use with this population is required.

Electronic supplementary material

The online version of this article (doi:10.1186/s12955-015-0338-x) contains supplementary material, which is available to authorized users.

The impact of structural and functional parameters in glaucoma patients on patient-reported visual functioning

BACKGROUND

To evaluate the impact of structural changes of the retinal nerve fiber layer (RNFL), and visual field loss, on functional impairment assessed by patient-reported visual functioning in glaucoma.

METHODS

Patients with glaucomatous optic nerve damage were enrolled in this cross-sectional study. Peripapillary RNFL thickness was obtained with spectral-domain optical coherence tomography (SD-OCT). Function was assessed by patient-reported visual functioning using the Rasch-calibrated Glaucoma Activity Limitation 9 (GAL-9) questionnaire and standard automated perimetry. The impact of peripapillary RNFL loss on functional impairment was analyzed with correlation and linear regression analyses.

RESULTS

A total of 176 eyes from 88 glaucoma patients were included. The SD-OCT assessed temporal-superior and temporal-inferior RNFL sector of the worse eye revealed significant correlation with the GAL-9 scores (r=-0.298, p=0.011 and r=-0.251, p=0.033, respectively). In mutivariate regression analysis, the best predictors for patient-reported visual functioning were visual acuity of the better eye and mean defect of the worse eye (R(2)=0.334), while structural parameters could not enhance the prediction of GAL-9 scores.

CONCLUSIONS

Self-reported visual functioning of patients with glaucoma is better predicted by visual performance data than structural parameters. However, some structural changes of the worse eye are significantly correlated with patient-reported visual functioning.

An alternative way to think about glaucoma screening, using a questionnaire as a tool, Chinese version

RATIONALE, AIMS AND OBJECTIVES

To develop a short screening test for the detection of preclinical glaucoma.

METHOD

This case-control study involved 690 participants aged 40 years or older: 338 patients with glaucoma or suspected glaucoma and 352 patients without glaucoma, who served as a control group. All participants were interviewed by a single trained research assistant. Patients' basic demographic and clinical information, past ophthalmic history and responses on the National Eye Institute 25-item Visual Function Questionnaire were collected. Two glaucoma-trained ophthalmologists examined all the participants using standard procedures to make a diagnosis. The biostatistical differences between the two groups were determined.

RESULTS

Five items were selected for glaucoma screening: 'Sense of worse vision compared with those of the same age', 'Ocular pain or discomfort during the past 6 months', 'History of cataract', 'Family history of glaucoma' and 'Hyperopia'. A score of 2 or more was used to define a group of positive cases with the most appropriate values for sensitivity (79.0%), specificity (76.7%) and predictive power (a positive predictive value of 76.5% and a negative predictive value of 79.2%).

CONCLUSION

A five-item instrument was developed to detect preclinical glaucoma. Anyone with a score of 2 or more may need further ophthalmic examination and treatment.

[Measurement of glaucoma-specific functionality with the GQL-15 and correlation with parameters of visual function]

INTRODUCTION

Glaucoma is one of the leading causes of irreversible blindness worldwide and can have a significant impact on patient quality of life and vision-related functioning. The Glaucoma Quality of Life 15 (GQL-15) questionnaire is a disease-specific instrument to evaluate and quantify functional impairment of patients with glaucoma. This study evaluated the German version of the GQL-15 including correlations with perimetric parameters.

METHODS

A German version of the GQL-15 containing 15 items was developed and evaluated in 98 patients with glaucoma in different stages of the disease. The GQL-15 results were correlated with the perimetric parameters mean deviation (MD) and pattern standard deviation (PSD) of the better and worse eye. Classical and probabilistic test analyses (Rasch model) were performed.

RESULTS

The mean GQL-15 value was 77.3 ± 21.7 (SD) and most items of the GQL-15 correlated significantly with the MD of the worse eye (r = -0.416; p = 0.0014) and the better eye (r = -0.304; p = 0.02). There was also a highly significant correlation between glaucoma-specific QoL and visual acuity. A short version containing nine items yielding a higher psychometric performance can also be used.

CONCLUSIONS

The German version of the GQL-15 is a potent instrument to evaluate impairment in vision-specific functioning of patients with glaucoma. The GQL-15 values are better correlated with the sensitivity of the eye with the more severe glaucomatous damage. The data can help for a better understanding of individual patient impairment to improve medical advice and therapy of patients with glaucoma.

Patient-reported outcomes (PRO's) in glaucoma: a systematic review

The aim of this review was to summarize literature in view of patient-reported outcome (PRO) instruments for glaucoma and provide guidance on how outcomes are best assessed based on evidence about their content and validity. A systematic literature review was performed on papers describing the developmental process and/or psychometric properties of glaucoma or vision-specific PRO-instruments. Each of them was assessed on their adherence to a framework of quality criteria. Fifty-three articles were identified addressing 27 PRO-instruments. In all, 18 PRO's were developed for glaucoma and 9 for diverse ophthalmologic conditions. Seven instruments addressed functional status, 11 instruments quality of life and 9 instruments disease and treatment-related factors. Most of the instruments demonstrated only partially adherence to predefined quality standards. The tools for assessing functional status were of poor quality, while the Glaucoma Quality of Life Questionnaire and the Vision Quality of Life Index were well-developed QoL measures, yet only validated using classical techniques. The Rasch-scaled QoL-tools, IVI and VCM1 need to improve their item-content for glaucoma patients. The questionnaires to measure adherence should improve their validity and the Treatment Satisfaction Survey for Intra Ocular Pressure pops out as the highest quality tool for measuring topical treatment side effects. This review revealed that most PRO-instruments demonstrated poor developmental quality, more specifically a lack of conceptual framework and item generation strategies not involving the patients' perspective. Psychometric characteristics were mostly tested using classical validation techniques.

Psychometric properties of the Greek NEI-RQL-42

Purpose

To evaluate the psychometric properties of the Greek National Eye Institute Refractive Error Quality of Life Questionnaire (NEI-RQL-42).

Methods

We developed the Greek version of the instrument using forward and backward translation. To examine reliability, Cronbach alpha for each subscale was used as an index of internal consistency. Test-retest reliability was evaluated with intraclass correlation coefficients (ICC). Regarding construct validity, both convergent and discriminant validities were calculated by means of multi-trait analysis. Furthermore, the instrument was evaluated by Rasch analysis, as well.

Results

Three patient groups were studied (emmetropes (n=20), myopes (n=41), and hyperopes (n=18)). Emmetropes scored significantly better in the majority of subscales, while myopes scored better than hyperopes in clarity of vision (p=0.012), near vision (p<0.001), and satisfaction with correction (p=0.001). Cronbach alpha ranged from 0.490 (glare) to 0.948 (expectations), with most subscales having high internal consistency. The ICCs ranged from 0.76 to 0.93 for all subscales. All items passed the convergent and discriminant validity tests. Strong correlations were detected between uncorrected visual acuity and near vision, expectations, activity limitations, dependence on correction, worry, and suboptimal correction subscales. Rasch analysis revealed potential weaknesses of the instrument that are associated with the assumptions of the model itself. Specifically, 3 items and 17.5% of the participants fell outside the tolerance box. Moreover, principal component analysis indicated average unidimensionality for the instrument.

Conclusions

Traditional validation methods indicate that the Greek NEI-RQL-42 scale has adequate psychometric properties for comparative studies in local populations. Rasch analysis indicates significant misfits to the model that should be taken into consideration and evaluated in future studies. These misfits might reflect inherent weaknesses of the original NEI-RQL-42 and not of its adaptation to Greek norms.

Is the pediatric quality of life inventory valid for use in preschool children with refractive errors?

PURPOSE

To determine the psychometric validity of the pediatric quality of life inventory (PedsQL 4.0) in assessing the impact of refractive errors on health-related quality of life (HRQoL) in preschool children in Singapore.

METHODS

Parents of toddlers (aged 25 to 48 months) and young children (49 to 72 months) completed the PedsQL 4.0, an HRQoL scale as part of population-based trial in Singapore. The outcome measures were the overall score, and the "physical"; "emotional"; "social"; and "school" functioning subscales. Rasch analysis was used to validate the PedsQL 4.0.

RESULTS

Parents of 939 (48.9%) toddlers and 982 (51.1%) young children completed the PedsQL 4.0 survey. The overall mean (±standard deviation) spherical equivalence for the right eye was 0.47 ± 1.13 diopter (D) for toddlers and 0.74 ± 1.22 D for young children. One hundred forty-nine (15.9%) toddlers and 90 (9.2%) young children were considered myopic (≥-0.50 D). Most participants (n = 1286, 89.6%) had presenting visual acuity 6/9 or better. Rasch analysis showed evidence of disordered category thresholds and poor person-item targeting for both groups. The separation reliability was 0.00 for toddlers and 0.03 for young children, indicating there was no variance in both samples. The PedsQL 4.0 overall and subscale scores displayed substantial multidimensionality as the variance values explained by the measures was <25% in both groups. A minimum value of 60% is usually considering acceptable.

CONCLUSIONS

The PedsQL 4.0 in its current state is not a valid psychometric scale to effectively evaluate the impact of refractive errors on HRQoL in preschool children in Singapore.

Choosing appropriate patient-reported outcomes instrument for glaucoma research: a systematic review of vision instruments

PURPOSE

To identify vision Patient-Reported Outcomes instruments relevant to glaucoma and assess their content validity.

METHODS

MEDLINE, MEDLINE in Process, EMBASE and SCOPUS (to January 2009) were systematically searched. Observational studies or randomised controlled trials, published in English, reporting use of vision instruments in glaucoma studies involving adults were included. In addition, reference lists were scanned to identify additional studies describing development and/or validation to ascertain the final version of the instruments. Instruments' content was then mapped onto a theoretical framework, the World Health Organization International Classification of Functioning, Disability and Health. Two reviewers independently evaluated studies for inclusion and quality assessed instrument content.

RESULTS

Thirty-three instruments were identified. Instruments were categorised into thirteen vision status, two vision disability, one vision satisfaction, five glaucoma status, one glaucoma medication related to health status, five glaucoma medication side effects and six glaucoma medication satisfaction measures according to each instruments' content. The National Eye Institute Visual Function Questionnaire-25, Impact of Vision Impairment and Treatment Satisfaction Survey-Intraocular Pressure had the highest number of positive ratings in the content validity assessment.

CONCLUSION

This study provides a descriptive catalogue of vision-specific PRO instruments, to inform the choice of an appropriate measure of patient-reported outcomes in a glaucoma context.

Relationships in glaucoma patients between standard vision tests, quality of life, and ability to perform daily activities

PURPOSE

To determine the relationships among three methods of assessing visual loss caused by glaucoma: (1) standard clinical tests of vision, (2) self-reported quality of life, and (3) the ability to perform activities of daily living.

METHODS

One hundred and ninety two glaucoma patients with a full range of glaucomatous visual loss were selected from the Glaucoma Service of Wills Eye Institute. Subjects were evaluated clinically by visual acuity, contrast sensitivity, visual field, stereopsis, the Disc Damage Likelihood Scale, and intraocular pressure. Subjects were evaluated subjectively by the 25-item National Eye Institute's Visual Functioning Questionnaire (NEI-VFQ-25) and objectively by a performance-based measure of visual function, the Assessment of Disability Related to Vision (ADREV). Statistical analysis, including Spearman coefficients, was performed on the data from the clinical measures, NEI-VFQ-25, and ADREV.

RESULTS

The clinical tests had higher correlations with ADREV than with the NEI-VFQ-25. There was a moderate, but not strong, connection between how patients rated their own visual ability with how they performed when objectively tested.

CONCLUSIONS

ADREV provides valid estimates of how visual loss due to glaucoma affects the ability to perform activities of daily living. Performance-based testing and quality of life evaluations are both independently important measures of health, which are related, but by no means the same.

Remediating serious flaws in the National Eye Institute Visual Function Questionnaire

PURPOSE

To test the assumption that the National Eye Institute Visual Function Questionnaire (NEI VFQ) measures visual functioning, assess the validity of its subscales, and, if flawed, revise the questionnaire and derive a shortened version with sound psychometric properties.

SETTING

Flinders Medical Centre, Adelaide, Australia.

METHODS

Patients from the cataract surgery waiting list self-administered and completed the 39-item NEI VFQ (NEI VFQ-39). Rasch analysis was applied, and the psychometric performance of the entire questionnaire and each subscale was tested. Instrument revision was performed in the context of Rasch analysis statistics.

RESULTS

Five hundred thirty-six patients (mean age 73.8 years) completed the questionnaire. Response categories for 2 question types were not used as intended so dysfunctional categories were combined. The NEI VFQ-39 and the 25-item version (NEI VFQ-25) had good precision but evidence of multidimensionality (more than 1 construct in 1 score), questions that did not fit the construct, suboptimum targeting of item difficulty to person ability, and dysfunctional subscales (8 NEI VFQ-39; 12 NEI VFQ-25). Questions could be reorganized into 2 constructs (a visual functioning scale and a socioemotional scale) that, after misfitting questions were removed, gave valid measurement of each construct and preserved 3 subscales. Removing redundancy from these long-form subscales yielded valid short-form scales.

CONCLUSIONS

Several NEI VFQ subscales were not psychometrically sound; as an overall measure, it is flawed by multidimensionality. This was repaired by segregation into visual functioning and socioemotional scales. Valid long and short forms of the scales could enhance application of the questionnaire.

Validation of the visual disability questionnaire (VDQ) in India

PURPOSE

To validate visual disability questionnaire (VDQ) in patients with low vision in India, and explore whether the two latent traits "importance" and "difficulty" associated with performance of daily activities are valid and independent constructs.

METHODS

The VDQ consisting of 25 items was administered verbally to 137 subjects with low vision aged 16 to 89 years. Responses for each item were rated for importance and difficulty using a 5-category Likert scale. Rasch analysis was used to estimate interval measures of response ratings.

RESULTS

Subjects could discriminate only three response categories for importance and difficulty. Content validity was demonstrated by good separation indices for importance (4.24 and 2.59 for the item and person parameters, respectively) and difficulty ratings (7.64 and 3.33, respectively). High reliability scores were recorded for importance (0.95 and 0.87) and difficulty ratings (0.98 and 0.92). The most important items were "grooming" (1.15 logits) and "reading newspaper" (0.97 logits). Although "threading a needle" was the least important item (-2.79 logits), it was the most difficult task (3.13 logits). The least difficult item was moving around in familiar places (-2.51 logits). A poor correlation was observed between the item measures (r = -0.19, p = 0.34) and also between person measures (r = 0.18, p = 0.03) of importance and difficulty.

CONCLUSIONS

The VDQ is a valid questionnaire with importance and difficulty ratings found to be independent constructs. This questionnaire could be used to prioritize the goals for rehabilitation intervention in patients with low vision.

An evaluation of the 10-item vision core measure 1 (VCM1) scale (the Core Module of the Vision-Related Quality of Life scale) using Rasch analysis

PURPOSE

To assess and re-engineer the Vision Core Measure 1 (VCM1) questionnaire in low vision (LV) and cataract participants using Rasch analysis.

METHODS

295 participants drawn from a low vision clinic and 181 from a cataract surgery waiting list completed the 10-item VCM1. Unidimensionality, item fit to the model, response category performance, differential item functioning (DIF) and targeting of items to patients were assessed. Category collapsing and item removal were considered to improve the questionnaire.

RESULTS

The initial fit of the VCM1 (combined populations) to the Rasch model showed lack of fit (chi2 = 83.3, df = 50, p = 0.002). There was evidence of DIF between the two populations which could not be resolved. Consequently, each population was assessed separately. Irrespective of the population, disordering of response category thresholds was evident. However, collapsing categories produced ordered thresholds and resulted in fit to the Rasch model for the LV (Total chi2 = 41.6, df = 30; p = 0.08) and cataract population (Total chi2 = 17.9, df = 20, p = 0.59). Overall, the VCM1 behaved as a unidimensional scale for each population and no item showed evidence of DIF. Item targeting to patients was however sub-optimal particularly for the cataract population.

CONCLUSION

The VCM1 questionnaire could be improved by shortening the response scale, although different response categories are required for cataract and LV populations. Calibration of items also differed across populations. While the VCM1 performs well within the Rasch model, in line with its initial purpose, it requires the addition of items to satisfactorily target low vision and cataract populations.

Psychometric properties of the Greek version of the NEI-VFQ 25

Background

To evaluate the reliability and construct validity of a Greek version of the NEI-VFQ-25 in patients with chronic ophthalmic diseases.

Methods

We developed the Greek version of the instrument using forward and backward translation. One hundred-eighty-six patients responded to the questionnaire. To examine reliability, Cronbach's alpha for each subscale was used as an index of internal consistency. Test-retest reliability was evaluated with intraclass correlation coefficients. Regarding construct validity, both convergent and discriminant validities were calculated by means of multi-trait analysis. Rasch analysis was used to estimate the visual ability required by each item for a particular response, and each patient's visual ability. Correspondingly, instrument validity was evaluated by estimating the distribution of residuals for item and subject measures.

Results

Four patient groups were studied, each including participants with a single cause of visual impairment. Group 1 consisted of 84 glaucoma subjects. Group 2 included 30 subjects with age-related macular degeneration (ARMD); group 3 included 25 subjects with dry-eye syndrome, whereas group 4 included 18 cataract patients. Twenty-nine healthy individuals comprised the control group. NEI-VFQ scores (mean ± SD) for the glaucoma, ARMD, dry-eye, cataract and control groups were: 76.9 ± 20.2, 70.9 ± 20.2, 81.6 ± 16.5, 73.5 ± 24.0 and 93.7 ± 8.9 respectively. Item analysis revealed no significant data skewing. Cronbach's alpha ranged from 0.678 to 0.926, with most subscales having high internal consistency. Intraclass correlation coefficient ranged from 0.717 to 0.910 for all subscales. All items passed the convergent and discriminant validity tests. Strong correlations were detected between visual acuity and "general vision", "distant activities" and "near activities" subscales. Significant correlations were also detected between visual field deficits and the "peripheral vision" and "general vision" subscales. Rasch analysis revealed potential weaknesses of the instrument that are associated with the assumptions of the model itself. Specifically, low precision of the "agreement" items was detected in the estimation of visual ability. Twenty-three percent of the subjects had fit statistics that fell outside the tolerance box.

Conclusion

Although traditional validation methods indicated that the Greek version of the NEI-VFQ-25 is a valid and reliable instrument for VS-QoL assessment, Rasch analysis detected significant misfits to the model, especially of the "agreement" items. This means that results of the corresponding subscales should be interpreted with extreme caution.

The Development, Assessment, and Selection of Questionnaires

Patient-reported outcome measurement has become accepted as an important component of comprehensive outcomes research. Researchers wishing to use a patient-reported measure must either develop their own questionnaire (called an instrument in the research literature) or choose from the myriad of instruments previously reported. This article summarizes how previously developed instruments are best assessed using a systematic process and we propose a system of quality assessment so that clinicians and researchers can determine whether there exists an appropriately developed and validated instrument that matches their particular needs. These quality assessment criteria may also be useful to guide new instrument development and refinement. We welcome debate over the appropriateness of these criteria as this will lead to the evolution of better quality assessment criteria and in turn better assessment of patient-reported outcomes.