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

HLS19-NAV-Validation of a New Instrument Measuring Navigational Health Literacy in Eight European Countries

To manoeuvre a complex and fragmented health care system, people need sufficient navigational health literacy (NAV-HL). The objective of this study was to validate the HLS19-NAV measurement scale applied in the European Health Literacy Population Survey 2019-2021 (HLS19). From December 2019 to January 2021, data on NAV-HL was collected in eight European countries. The HLS19-NAV was translated into seven languages and successfully applied in and validated for eight countries, where language and survey method differed. The psychometric properties of the scale were assessed using confirmatory factor analysis (CFA) and Rasch modelling. The tested CFA models sufficiently well described the observed correlation structures. In most countries, the NAV-HL data displayed acceptable fit to the unidimensional Rasch partial credit model (PCM). For some countries, some items showed poor data-model fit when tested against the PCM, and some items displayed differential item functioning for selected person factors. The HLS19-NAV demonstrated high internal consistency. To ensure content validity, the HLS19-NAV was developed based on a conceptual framework. As an estimate of discriminant validity, the Pearson correlations between the NAV-HL and general health literacy (GEN-HL) scales were computed. Concurrent predictive validity was estimated by testing whether the HLS19-NAV, like general HL measures, follows a social gradient and whether it forms a predictor of general health status as a health-related outcome of general HL. In some countries, adjustments at the item level may be beneficial.

Surgical management of anterior clinoidal meningiomas: consensus statement on behalf of the EANS skull base section

BACKGROUND

The optimal management of clinoidal meningiomas (CMs) continues to be debated.

METHODS

We constituted a task force comprising the members of the EANS skull base committee along with international experts to derive recommendations for the management of these tumors. The data from the literature along with contemporary practice patterns were discussed within the task force to generate consensual recommendations.

RESULTS AND CONCLUSION

This article represents the consensus opinion of the task force regarding pre-operative evaluations, patient's counselling, surgical classification, and optimal surgical strategy. Although this analysis yielded only Class B evidence and expert opinions, it should guide practitioners in the management of patients with clinoidal meningiomas and might form the basis for future clinical trials.

A Scoping Review of Quality of Life Questionnaires in Glaucoma Patients

PRECIS

Multiple questionnaires exist to measure glaucoma's impact on quality of life (QoL). Selecting the right questionnaire for the research question is essential, as is patients' acceptability of the questionnaire to enable collection of relevant patient-reported outcomes.

PURPOSE

QoL relating to a disease and its treatment is an important dimension to capture. This scoping review sought to identify the questionnaires most appropriate for capturing the impact of glaucoma on QoL.

METHODS

A literature search of QoL questionnaires used in glaucoma, including patient-reported outcomes measures, was conducted and the identified questionnaires were analyzed using a developed quality criteria assessment.

RESULTS

Forty-one QoL questionnaires were found which were analyzed with the detailed quality criteria assessment leading to a summary score. This identified the top 10 scoring QoL questionnaires rated by a synthesis of the quality criteria grid, considering aspects such as reliability and reproducibility, and the authors' expert clinical opinion. The results were ratified in consultation with an international panel of ophthalmologists (N=49) from the Educational Club of Ocular Surface and Glaucoma representing 23 countries.

CONCLUSIONS

Wide variability among questionnaires used to determine vision related QoL in glaucoma and in the responses elicited was identified. In conclusion, no single existing QoL questionnaire design is suitable for all purposes in glaucoma research, rather we have identified the top 10 from which the questionnaire most appropriate to the study objective may be selected. Development of a new questionnaire that could better distinguish between treatments in terms of vision and treatment-related QoL would be useful that includes the patient perspective of treatment effects as well as meeting requirements of regulatory and health authorities. Future work could involve development of a formal weighting system with which to comprehensively assess the quality of QoL questionnaires used in glaucoma.

Everyday visual demands of people with low vision: A mixed methods real-life recording study

Research has demonstrated that low vison aids (LVAs) can have a positive impact on the functional sight of those living with sight loss. Step changes in technology are now enabling new wearable LVAs with greater potential than those available previously. For these novel devices to receive increased acceptance and therefore adoption by those with sight loss, visual task demands have to be understood more clearly in order to enable better alignment between device design and user requirements. The aim of this study was to quantify these requirements. Thirty-two participants aged 18 to 87 wore a spectacle-mounted video camera to capture and narrate all everyday situations in which they would use a “perfect” sight aid during 1 week. Captured scenes were analyzed through categorization and computational image analysis. Results showed large variation in activities and lifestyles. Participants reported no available sight aid or coping strategy for 57% of the recorded activities. Reading made up 49% of all recorded tasks, the other half comprising non-textual information. Overall, 75% of captured activities were performed ad hoc (duration of 0–5 minutes), 78% occurred indoors, 58% occurred at home, 48% were lit by natural light, 68% included the object of interest within reach, and 69% required a single focus plane only. Around half of captured objects of interest had a size of 2 degrees visual angle (2.08 logarithm of the minimum angle of resolution [logMAR]) or smaller. This study highlights the need for a sight aid that can make both textual and non-textual scenes accessible while offering flexibility to accommodate individual lifestyles.

The feasibility and effects of eye movement training for visual field loss after stroke: a mixed methods study

Introduction

Visual field loss affects around 20% of stroke survivors, reducing quality of life. Eye movement training is a promising rehabilitation method, and several different interventions are used by occupational therapists. This study aimed to explore the feasibility and effects of four eye movement training interventions for stroke survivors with visual field loss.

Method

A mixed methods study – quantitative n-of-1 with qualitative interviews. The participants were 11 home-dwelling stroke survivors with visual field loss. The interventions used were MyHappyNeuron, NVT, Rainbow Readers and VISIOcoach, delivered in a randomised order. Visual search, reading speed, activities of daily living and quality of life were assessed three times before intervention use, then immediately after each intervention; these were analysed visually. A final semi-structured interview was then analysed using framework methods.

Results

Evidence of effect was divergent. Quantitatively there was no measured effect, but qualitatively participants reported benefits in visual skills, daily life skills and emotions, which varied by intervention. Median training time was 3–4 hours (range 0.5–6.5) for NVT, Rainbow Readers and MyHappyNeuron, and 9.5 hours (range 2.3–16.8) for VISIOcoach.

Conclusion

Eye movement training interventions were feasible for stroke survivors at home. Qualitative evidence suggests that variations in the eye movements trained and delivery modality underlie variations in perceived effect.

Validation and application of Catquest-9SF in various populations: A systematic review

Cataract is a common cause of reversible blindness. Visual acuity alone is not enough to assess appropriateness for surgery, prioritization, and outcomes. Catquest-9SF questionnaire evaluates patients' self-assessed visual function as related to daily tasks. We summarize and assess the validity of Catquest-9SF as a patient-reported outcome questionnaire to determine its suitability for clinical use. Thirteen studies with sample sizes ranging 102-10,886 (total n = 15,289) undertaken from 2009 to 2018 were included. Catquest-9SF showed unidimensionality, ordered response thresholds, and acceptable precision in all studies. Nine studies had significant mistargeting (range 0.66 to -2.04); the tasks being easy relative to the respondent ability in most studies. Two studies had misfitting items. We conclude Catquest-9SF is a valid and reliable tool to measure visual function in patients with cataract in various populations. Because results can be population specific, it is recommended that Catquest-9SF be validated in a new population before it is incorporated in routine practice.

An alternative application of Rasch analysis to assess data from ophthalmic patient-reported outcome instruments

Purpose

To highlight the potential shortcomings associated with the current use Rasch analysis for validation of ophthalmic questionnaires, and to present an alternative application of Rasch analysis to derive insights specific to the cohort of patients under investigation.

Methods

An alternative application of Rasch analysis was used to investigate the quality of vision (QoV) for a cohort of 481 patients. Patients received multifocal intraocular lenses and completed a QoV questionnaire one and twelve months post-operatively. The rating scale variant of the polytomous Rasch model was utilized. The parameters of the model were estimated using the joint maximum likelihood estimation. Analysis was performed on data at both post-operative assessments, and the outcomes were compared.

Results

The distribution of the location of symptoms altered between assessments with the most annoyed patients completely differing. One month post-operatively, the most prevalent symptom was starbursts compared to glare at twelve months. The visual discomfort from the most annoyed patients is substantially higher at twelve months. The current most advocated approach for validating questionnaires using Rasch analysis found that the questionnaire was “Rasch-valid” one month post-operatively and “Rasch-invalid” twelve months post-operatively.

Conclusion

The proposed alternative application of Rasch analysis to questionnaires can be used as an effective decision support tool at population and individual level. At population level, this new approach enables one to investigate the prevalence of symptoms across different cohorts of patients. At individual level, the new approach enables one to identify patients with poor QoV over time. This study highlights some of the potential shortcomings associated with the current use of Rasch analysis to validate questionnaires.

Rasch Analysis of the Standard Patient Evaluation of Eye Dryness Questionnaire

BACKGROUND

This study sought to investigate, if the Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire acts as a measure of dry eye severity and whether it is unidimensional using Rasch analysis.

METHODS

This is a hospital-based cross-sectional study. The study included 127 patients with glaucoma with either a clinical diagnosis of dry eye or an Ocular Surface Disease Index score of ≥13. Participants completed questionnaires (SPEED) delivered directly to them.

RESULTS

A total of 127 participants met the inclusion criteria and were included in the analysis. Category response analysis revealed that the average logit measures for the response category increased with higher response category from -4.93 to +5.41 logit. Item infit mean square statistics of the individual items ranged from 0.57 to 1.33, with a mean of 0.99±0.2. The individual item outfit mean square ranged from 0.58 to 1.36, with a mean of 1.02±0.0. The person separation index (PSI) and separation reliability of the SPEED were 2.23 and 0.83, respectively. Principal component analysis (PCA) of the standardized model residuals revealed evidence of multidimensionality, with first contrast eigenvalue of 2.5 and the second contrast eigenvalue of 1.7. Because fit statistics of all items were within 0.5 to 1.7 and considered adequate for clinical observations, no item was removed. However, the six items of the SPEED that asked about the commonest dry eye symptoms as reported by patients with dry eye were analyzed separately to determine how they behaved. The item fit statistics of these six items were within the range of 0.6 to 1.4. The outfit statistics range from 0.62 to 1.26, with a mean of 1.00±0.1. The infit statistics range from 0.61 to 1.24, with a mean of 0.99±0.2. The PSI and reliability were 2.2 and 0.83, respectively. Finally, PCA of the standardized model residuals revealed no evidence of multidimensionality, with first contrast eigenvalue of 2.0.

CONCLUSION

In summary, this study showed that the SPEED had an ordered response category and was a measure of dry eye severity. However, PCA of the standardized model residuals revealed evidence of multidimensionality. A proposed six-item SPEED was unidimensional and was also a measure of disease severity. Hence, the SPEED questionnaire score may be used as a measure of dry eye severity in clinical practice and epidemiological studies.

Psychosocial interventions to improve mental health in adults with vision impairment: systematic review and meta-analysis

PURPOSE

To systematically assess the literature on psychosocial interventions to improve mental health (i.e. depression, anxiety, mental fatigue, loneliness, psychological stress and psychological well-being) in visually impaired adults (≥18 years).

METHODS

The databases Medline, Embase and Psychinfo were searched for relevant studies, which were categorised into randomised controlled trials (RCTs), non-RCTs and before and after comparisons (BA). The Cochrane Collaboration Risk of Bias Tool was used to assess study quality. Standardised mean differences (SMD) were calculated to quantitatively summarise the outcomes of the RCTs and non-RCTs in a meta-analysis. Meta-regression was used to explore sources of heterogeneity in the data.

RESULTS

The search identified 27 papers (published between 1981 and 2015), describing the outcomes of 22 different studies (14 RCTs, four non-RCTs, and four BAs). Pooled analyses showed that interventions significantly reduced depressive symptoms (SMD -0.30, 95% confidence interval (CI) -0.60 to -0.01), while effects on anxiety symptoms, mental fatigue, psychological stress and psychological well-being were non-significant. Meta-regression analyses showed homogeneity in effect sizes across a range of intervention, population, and study characteristics. Only a higher age of participants was associated with less effective results on depressive symptoms (b = 0.03, 95% CI 0.01 to 0.05), psychological stress (b = 0.07, 95% CI 0.01 to 0.13) and psychological well-being (b = -0.03, 95% CI -0.05 to 0.01). However, after removing a clear outlier the overall effect on depressive symptoms and the influence of age on depressive symptoms and psychological stress were no longer significant, while the influence of age on psychological well-being remained.

CONCLUSIONS

There is currently only limited evidence for the effectiveness of psychosocial interventions in the field of low vision. More well-designed trials are needed with specific attention for interventions tailored to the needs of elderly patients.

Developing an Item Bank to Measure Quality of Life in Individuals With Glaucoma, and the Results of the Interview With Patients: The Effect of Visual Function, Visual Field Progression Rate, Medical, and Surgical Treatments on Quality of Life

PURPOSE

To construct a new item bank to measure quality of life (QOL) in glaucoma patients and to evaluate glaucoma patients' QOL using the item bank.

METHODS

An item bank of questions was generated through a literature review of QOL instruments useful for glaucoma patients. Using this item bank, a cognitive survey was performed on 203 patients with glaucoma (112 males and 91 females, 61.9±11.9 y old; mean±SD). The results were then analyzed using the Rasch analysis, and the Rasch-derived disability scores were predicted using linear modelling and the following clinical parameters: age, mean total deviation (mTD) in superior and inferior visual field (mTDsup/mTDinf), mTD progression rate, better visual acuity, worse visual acuity, number of eye drops administered per day, number of trabeculectomy procedures experienced in both eyes.

RESULTS

A total of 23 questionnaires of QOL in glaucoma patients were identified resulting in an item bank of 187 questions related to the following tasks: reading/writing, walking, going out, eating and driving (direct disability) as well as questions concerned with worry/anxiety, social participation, and physical symptoms (indirect disability). In the optimal model for direct disability, age and mTDinf were identified as significant predictors, whereas number of eye drops administered per day and number of trabeculectomy experienced were included in the optimal model for indirect disability.

CONCLUSIONS

A new item bank to measure QOL in glaucoma patients was developed and evaluated. Age and mTDinf were found to be related to direct disability while medical and surgical treatments were related to indirect disability.

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.

Measuring coping in parents of children with disabilities: a rasch model approach

Background

Parents of a child with disability must cope with greater demands than those living with a healthy child. Coping refers to a person’s cognitive or behavioral efforts to manage the demands of a stressful situation. The Coping Health Inventory for Parents (CHIP) is a well-recognized measure of coping among parents of chronically ill children and assesses different coping patterns using its three subscales. The purpose of this study was to provide further insights into the psychometric properties of the CHIP subscales in a sample of parents of children with disabilities.

Methods

In this cross-sectional study, 220 parents (mean age, 33.4 years; 85% mothers) caring for a child with disability enrolled in special schools as well as in mainstream schools completed the 45-item CHIP. Rasch analysis was applied to the CHIP data and the psychometric performance of each of the three subscales was tested. Subscale revision was performed in the context of Rasch analysis statistics.

Results

Response categories were not used as intended, necessitating combining categories, thereby reducing the number from 4 to 3. The subscale – ‘maintaining social support’ satisfied all the Rasch model expectations. Four item misfit the Rasch model in the subscale –maintaining family integration’, but their deletion resulted in a 15-item scale with items that fit the Rasch model well. The remaining subscale – ‘understanding the healthcare situation’ lacked adequate measurement precision (<2.0 logits).

Conclusions

The current Rasch analyses add to the evidence of measurement properties of the CHIP and show that the two of its subscales (one original and the other revised) have good psychometric properties and work well to measure coping patterns in parents of children with disabilities. However the third subscale is limited by its inadequate measurement precision and requires more items.

Identifying content for the glaucoma-specific item bank to measure quality-of-life parameters

PURPOSE

Patient-reported outcomes (PROs) have become essential clinical trial end points. However, a comprehensive, multidimensional, patient-relevant, and precise glaucoma-specific PRO instrument is not available. Therefore, the purpose of this study was to identify content for a new, glaucoma-specific, quality-of-life (QOL) item bank.

METHODS

Content identification was undertaken in 5 phases: (1) identification of extant items in glaucoma-specific instruments and the qualitative literature; (2) focus groups and interviews with glaucoma patients; (3) item classification and selection; (4) expert review and revision of items; and (5) cognitive interviews with patients.

RESULTS

A total of 737 unique items (extant items from PRO instruments, 247; qualitative articles, 14 items; focus groups and semistructured interviews, 476 items) were identified. These items were classified into 10 QOL domains. Four criteria (item redundancy, item inconsistent with domain definition, item content too narrow to have wider applicability, and item clarity) were used to remove and refine the items. After the cognitive interviews, the final minimally representative item set had a total of 342 unique items belonging to 10 domains: activity limitation (88), mobility (20), visual symptoms (19), ocular surface symptoms (22), general symptoms (15), convenience (39), health concerns (45), emotional well-being (49), social issues (23), and economic issues (22).

CONCLUSIONS

The systematic content identification process identified 10 QOL domains, which were important to patients with glaucoma. The majority of the items were identified from the patient-specific focus groups and semistructured interviews suggesting that the existing PRO instruments do not adequately address QOL issues relevant to individuals with glaucoma.

Evaluation of an emotional support service for the visually impaired

PURPOSE

To evaluate the impact of a facilitated peer group emotional support service on visual quality of life (VQoL).

METHODS

Consecutive participants in an emotional support service delivered to groups of up to six and facilitated by trained counselors were recruited (n = 29). The VCM1 (Vision Quality-of-life Core Measure) instrument was administered to participants at the start of the service, at the end of the service, and 6 months after completion of the service.

RESULTS

For the group as a whole, VQoL significantly improved between the beginning of the service and the end (F(1,23) = 16.43, p = 0.000) but was no better than at the start 6 months later (F(1,23) = 3.60, p = 0.07). However, those with poorer initial VQoL showed significantly greater improvements after 6 months (1.74 ± 2.21 logits) than those with higher initial VQoL (-0.12 ± 0.71 logits) (t23 = 2.89, p = 0.008). The effect size of the intervention for those with poor initial VQoL was 1.10 at the end of service and 0.92 after 6 months. The items that became and remained easier were "feeling lonely or isolated due to eyesight," "feeling sad or low due to eyesight," and "feeling worried about general safety outside the home."

CONCLUSIONS

This facilitated peer group emotional support service significantly improves VQoL as assessed with the VCM1 over at least 6 months for those with poorer initial VQoL. Different interventions may be needed for those with initially good VQoL and to improve other aspects of QoL not influenced by the service.

The impact of cataract, cataract types, and cataract grades on vision-specific functioning using Rasch analysis

PURPOSE

To determine the impact of cataracts and their types and grades on vision-specific functioning.

DESIGN

Prospective population-based cross-sectional study.

METHODS

The Singapore Indian Eye Study examined 3400 of 4497 (75.6% response rate) ethnic Indians 40 years of age and older living in Singapore. Three thousand one hundred sixty-eight (93.2%) fulfilled inclusion criteria with complete information for final analysis. Cataracts were assessed on slit-lamp examination and were graded according to the Lens Opacity Classification System III. Vision-specific functioning scores were explored with the Visual Function scale, validated using Rasch analysis.

RESULTS

Two hundred sixty-nine (8.5%) and 740 (23.4%) of the study participants had unilateral and bilateral cataracts, respectively, and 329 (10.4%), 800 (25.2%), and 128 (4.1%) participants had nuclear, cortical, and posterior subcapsular (PSC) cataracts, respectively. In multivariate linear regression models, the presence of bilateral rather than unilateral cataract (β = -0.12; 95% confidence interval, -0.20 to 0.00) was associated independently with poorer vision-specific functioning, even after adjusting for undercorrected refractive error (β = -0.11; 95% confidence interval, -0.21 to 0.00). Bilateral nuclear, cortical, and PSC cataracts also were associated with poorer vision-specific functioning (β = -0.31, -0.15, and -1.15, respectively), with combinations of them having even greater impact. Significantly poorer vision-specific functioning occurred at Lens Opacity Classification System grades 4 (nuclear opalescence), 5 (nuclear color), 3 (cortical), and 1 (PSC) or higher.

CONCLUSIONS

People with bilateral but not unilateral cataracts experience difficulty with performing vision-specific daily activities independent of refractive error, with PSC cataracts and cataract combinations having the greatest impact. Cataract types cause poorer vision-specific functioning beginning at different severity grades.

Application of the Rasch model to develop a simplified version of a multiattribute utility measurement on attitude toward labor epidural analgesia

BACKGROUND

Valid and reliable measures based on health behavior theory, such as multiattribute utility decision theory, are essential to elucidate complex relationships between psychological factors and labor pain. In this study we aimed to use Rasch analysis to simplify a previously developed 20-item multidimensional questionnaire on attitude toward labor epidural analgesia using multiattribute utility theory.

METHODS

The Rasch analysis was performed to condense item selection categories, to exclude misfit items and persons, and to generate a unidimensional attitude toward labor epidural analgesia (ATLEA) score. Item characteristics and thresholds of rating categories in the questionnaire were also estimated. Reliability and empirical validity of the simplified version were further compared with those of the full version.

RESULTS

One hundred sixty-seven postpartum women completed the questionnaire. The original 10 rating scale categories were combined to make 4 without compromising reliability. Three respondents and 11 items were excluded because of misfit. Reliability indices of the simplified and full versions were 0.68 and 0.74, respectively. The correlation coefficient between ATLEA scores from the simplified and full versions was 0.89. Empirical validity values of ATLEA scores from the simplified and full versions for labor epidural analgesia decision, as assessed by area under the receiver operating characteristic curves, were 0.80 and 0.81, respectively.

CONCLUSIONS

We demonstrated application of the Rasch analysis to simplifying a multiattribute utility questionnaire without compromising reliability. Further study is necessary to determine whether the simplified questionnaire is valid for use in clinical practice.

Re-evaluating a vision-related quality of life questionnaire with item response theory (IRT) and differential item functioning (DIF) analyses

BACKGROUND

For the Low Vision Quality Of Life questionnaire (LVQOL) it is unknown whether the psychometric properties are satisfactory when an item response theory (IRT) perspective is considered. This study evaluates some essential psychometric properties of the LVQOL questionnaire in an IRT model, and investigates differential item functioning (DIF).

METHODS

Cross-sectional data were used from an observational study among visually-impaired patients (n = 296). Calibration was performed for every dimension of the LVQOL in the graded response model. Item goodness-of-fit was assessed with the S-X(2)-test. DIF was assessed on relevant background variables (i.e. age, gender, visual acuity, eye condition, rehabilitation type and administration type) with likelihood-ratio tests for DIF. The magnitude of DIF was interpreted by assessing the largest difference in expected scores between subgroups. Measurement precision was assessed by presenting test information curves; reliability with the index of subject separation.

RESULTS

All items of the LVQOL dimensions fitted the model. There was significant DIF on several items. For two items the maximum difference between expected scores exceeded one point, and DIF was found on multiple relevant background variables. Item 1 'Vision in general' from the "Adjustment" dimension and item 24 'Using tools' from the "Reading and fine work" dimension were removed. Test information was highest for the "Reading and fine work" dimension. Indices for subject separation ranged from 0.83 to 0.94.

CONCLUSIONS

The items of the LVQOL showed satisfactory item fit to the graded response model; however, two items were removed because of DIF. The adapted LVQOL with 21 items is DIF-free and therefore seems highly appropriate for use in heterogeneous populations of visually impaired patients.

The impact of cataract surgery questionnaire: re-evaluation using Rasch analysis

PURPOSE

The Impact of Cataract Surgery (ICS) questionnaire was designed to assess cataract surgery outcomes. The aim of this study was to describe the psychometric properties of the ICS questionnaire using the Rasch model in a cataract population.

METHODS

Ninety-one patients waiting to undergo cataract surgery in the first or second eye at the Flinders Medical Centre, Adelaide, South Australia self-administered the four-item ICS questionnaire. Rasch analysis was performed to assess behaviour of response categories, ability to differentiate between participants' visual abilities (person separation; minimum acceptable 2.0), if items measure a single underlying construct [i.e. unidimensionality assessed by fit statistics and further by principal components analysis (PCA)] and matching of item difficulty to participant ability (targeting; ideal < 0.5 logits). Adequate person separation was defined as basic requirement for a measure, failing which further assessment such as PCA was not performed.

RESULTS

The four-item ICS questionnaire did not meet the required measurement properties (person separation zero). Response categories did not behave as intended, requiring the collapsing of categories for one item (read ordinary newspaper-size print). One item misfit (estimating distance) indicating that it was not measuring the same construct as other items. However, person separation failed to improve following the deletion of this item. Targeting was -0.46 logits, indicating that the item difficulty was well suited to the visual abilities of the participants.

CONCLUSION

In its present form, the ICS is unsuitable for visual disability assessment in patients awaiting cataract surgery. Other, better visual function questionnaires are available and preferred.

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.

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.