Are standard instruments valid for the assessment of quality of life and symptoms in glaucoma?

PURPOSE: To determine if the impact of Visual Impairment Instrument (IVI) and Glaucoma Symptom Scale (GSS) are valid instruments to assess participation in daily living and ophthalmic complaints, respectively, in a glaucoma population. METHODS: Patients with glaucoma were recruited from private and public clinics and completed the IVI and GSS questionnaires. The two scales were assessed for fit to the Rasch model. Unidimensionality, individual item and person fit to the model, response category performance (how respondents differentiate between the response options), differential item functioning (how subgroups, despite equal levels of the underlying trait, respond differently to an individual item), and targeting of items to patients (good spread of items across the full range of patients' scores) were assessed. RESULTS: One hundred seventy-five participants (mean age = 71 year) were recruited. The majority (65%) had primary open angle glaucoma and good presenting visual acuity >or=6/9 in the better eye (87%). Only one-third of the participants had severe visual field loss in both eyes. Disordered thresholds were evident across all GSS items, indicating that the categories were difficult to discriminate and required category collapsing (5 to 3 categories). There was no evidence of person and item misfit, differential item functioning, and multidimensionality. However, both scales displayed ineffective person-item targeting as a large number of participants demonstrated little difficulty with the most difficult items. CONCLUSIONS: Because of unsatisfactory targeting, The IVI and GSS are suboptimal scales to assess patients with glaucoma but relatively good vision. It is likely that items could be added to optimize the performance of both instruments. There may however be a need to develop a glaucoma-specific instrument to assess Quality of Life in this population.     

Psychometric properties of visual functioning index using Rasch analysis

Acta Ophthalmol. 2010: 88: 797–803

Abstract.

Purpose: The visual functioning index (VFI) was one of the first questionnaires developed using classical test theory to assess outcomes of cataract surgery. However, it was not Rasch‐validated. The objective of this study was to examine the psychometric properties of the VFI using Rasch analysis in patients with cataract. Methods: The 11‐item VFI was self‐administered to 243 patients (mean age 73.9 years) drawn from a cataract surgery waiting list. We examined the response category thresholds, item fit statistics, differential item functioning and unidimensionality for the VFI and its three subscales. Results: Category thresholds were ordered. The person separation and reliability were low, indicating the poor discriminatory ability of the VFI. No items misfit but there was suboptimal targeting of item difficulty to patient ability. On the whole the items in the VFI were too easy for the sample. Only one item showed moderate differential item functioning. Conclusion: The VFI does not meet the stringent requirements of the Rasch model. However adding more items to suit the more able patients with cataract as well as those awaiting second‐eye cataract surgery could optimize the VFI.     

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.     

Catquest questionnaire: re-validation in an Australian cataract population

Background:  The Catquest questionnaire was developed using traditional methodology to enable cataract surgery outcomes assessment in European countries. Recently, it has been validated using Rasch analysis in a Swedish population resulting in the Catquest-9SF. The aim of the present study was to assess the performance of the Catquest and the Catquest-9SF questionnaires using Rasch analysis in Australian cataract patients.
Methods:  A total of 217 cataract patients awaiting surgery at Flinders Medical Centre, Adelaide, South Australia self-administered the Catquest questionnaire. This is a 19-item instrument containing frequency, difficulty, symptoms and global rating items. Rasch analysis was undertaken to assess the unidimensionality (whether all the items are measuring a single underlying construct using principal components analysis or PCA), person separation (ability of the questionnaire to distinguish between strata of patient ability) and targeting of item difficulty to person ability.
Results:  Similar to the previous validation study, the original Catquest questionnaire required revision because of misfit and multidimensionality necessitating removal of the frequency items. The revised version was similar to the Catquest-9SF although an extra driving item was a valid optional inclusion. The Catquest-9SF performed well in the Australian cohort satisfying all criteria for valid measurement including unidimensionality. However, targeting of item difficulty to person ability was marginally worse compared with the Swedish cataract population indicating the Australian cataract patients present for surgery at lower levels of visual disability.
Conclusions:  The Catquest-9SF is a reliable and valid measure of visual disability in the Australian cataract population.     

The Impact of Vision Impairment Questionnaire: an evaluation of its measurement properties using Rasch analysis

PURPOSE: To explore the psychometric properties of the Impact of Vision Impairment scale (IVI) by using Rasch analysis. METHODS: Three hundred fourteen first-time referrals to low-vision clinics completed the 32-item IVI. The data were Rasch-analyzed with a partial credit model using RUMM2020 software (RUMM Laboratory, Perth, WA, Australia). The overall fit of the model, response scale, individual item fit, differential item functioning, unidimensionality, and person-separation reliability were assessed. RESULTS: Initially, 26 items displayed disordered thresholds. However, collapsing the response scale to three categories (4 items) and four categories (28 items) produced ordered response thresholds for all items. Four items with high proportions of missing responses, poor spread, high skewness, and deviation between observed and expected model curves were then removed. This adjustment produced overall fit to the Rasch model (item-trait interaction chi(2) = 118.3; P = 0.32). The final mean (SD) person and item fit residuals ere 0.06 (0.85) and -0.20 (1.45), respectively. The person-separation reliability was 0.9, indicating that the scale was able to discriminate between several different groups of participants. The revised scale was well targeted to the participants, with similar mean locations for items (0.00) and persons (0.16). A significant difference between participants of mild, moderate, and severe visual impairment (ANOVA; P 0.001) supported the criterion validity of the Rasch-scaled IVI. CONCLUSIONS: The results provide support for the measurement properties of the Rasch-scaled 28-item version of the IVI and of its potential for assessing outcomes of low-vision rehabilitation. A raw score-to-Rasch person measure conversion is supplied.     

The outcome of cataract surgery measured with the Catquest‐9SF

Purpose: The purpose of this study was to use the Catquest‐9SF to measure cataract surgery outcomes, and to use Rasch analysis to test the psychometric properties of this questionnaire, including its validity and responsiveness. Methods: Patients were recruited as consecutive cataract surgery patients during 1 month at six surgical units in Sweden (via the National Cataract Register). The patients completed the questionnaire before surgery and 3 months after. The Catquest‐9SF data were assessed for fit to the Rasch model using version 3.63.2 of the WINSTEPS software (Winsteps.com, Beaverton, OR, USA). Both preoperative and postoperative questionnaires were included in the analysis. The responsiveness to cataract surgery was calculated as the effect size. Results: Completed questionnaires before and after surgery were received from 846 patients. The Rasch analysis showed that the category thresholds were ordered. All items fit a single overall construct (infit range 0.79–1.40; outfit range 0.74–1.40). The ability to discriminate different strata of person ability was good, with a real patient separation of 2.58 and patient separation reliability of 0.87. The questionnaire showed unidimensionality and was largely free from differential item functioning. The item difficulty was reasonably well targeted to both preoperative and postoperative patient ability. The Catquest‐9SF Rasch score correlated significantly with visual acuity, and cataract surgery resulted in a significant improvement with an effect size of 1.8. Conclusion: The Catquest‐9SF shows excellent psychometric properties, as demonstrated by Rasch analysis. It is highly responsive to cataract surgery, and its brevity (nine items) makes it well suited for use in daily clinical practice.     

The impact of vision impairment questionnaire: an assessment of its domain structure using confirmatory factor analysis and rasch analysis

PURPOSE: To assess and validate the subscale structure of the 28-item Impact of Visual Impairment (IVI) Scale by using confirmatory factor analysis (CFA) and Rasch analysis for use as an outcome measure. METHODS: Three hundred nineteen participants completed the IVI questionnaire, and the responses then were subjected to Rasch analysis by RUMM2020 software. With the person estimates for each item, CFA was used to assess two hypothesized structures: three-and four-factor models. The subscales of the model with the best fit were then further validated by Rasch analysis. RESULTS: CFA supported a three-factor model that included items from the emotional well-being, reading and accessing information, and mobility and independence subscales. Almost all the selected goodness-of-fit statistics for the three-factor model were better than the recommended values. The factor loadings of the items on their respective domains were all statistically significant (P < 0.001) and ranged between 0.54 and 0.81. The three subscales individually fitted the Rasch model according to the item-trait interaction test (mobility and independence chi(2) [df] = 45.9 [44], P = 0.39; emotional well-being = 28.4 [32], P = 0.65; and reading and accessing information = 43.5 [36], P = 0.18). The item-fit residuals values of the three subscales were <2.5 and showed mean and standard deviations approximating 0 and 1, respectively. The internal consistency reliability of the subscales (alpha) was substantial, ranging between 0.89 and 0.91. CONCLUSIONS: An examination of the IVI dimension confirmed a three-subscale structure that displays interval measurement characteristics likely to provide a valid and reliable assessment of restriction of participation. The findings provide an opportunity for a more detailed measurement of the effects of different types of low-vision rehabilitation programs.     

白内障患者报告结局条目库的研制

目的:基于Rasch模型研制白内障患者报告结局(PROs)条目库,为准确、全面和动态评估白内障PROs奠定基础.方法:横断面调查研究.根据纳入标准选取我院已确诊的白内障住院患者,采用本课题组前期基于循证医学方法构建的白内障PROs条目池对其进行问卷调查.通过Rasch分析各维度条目选项概率曲线(CPC)、测量精密性、条目拟合指标(infit/outfit MNSQ)、单维性、匹配度和条目功能差异(DIF)等测量特性指标,并反复迭代、提炼,直至得到测量特性优良的条目.采用Pearson相关分析评估各维度和视力的相关性.结果:共纳入296例白内障患者,其中男130例,女166例,年龄70(63,77)岁,受过小学及以上教育者178例(60.1%),术前双眼日常生活视力(LogMAR)为0.0~3.0,中位数为0.6.条目库共纳入3个维度,其中视觉相关活动受限维度23个条目,视觉症状维度14个条目,精神心理健康11个条目,所有条目选项数量均为4个.视觉相关活动受限维度中,选项类别阈值分别为-1.84、0.04、1.79,被试分离信度/被试分离系数(PSR/PSI)为0.93/3.59,主成分分析(PCA)第一成分未解释方差特征值为2.61,匹配度为-0.81,DIF值均小于1;该维度得分与好眼视力(r=0.619,P<0.01)和双眼视力(r=0.622,P<0.01)有相关性.视觉症状维度中,选项类别阈值分别为-1.83、-0.18、2.00,PSR/PSI为0.88/2.68,PCA第一成分未解释方差特征值为2.53,匹配度为-1.35,2个条目在眼部并发症方面的DIF值大于1,其余DIF值均小于1;该维度得分与好眼视力(r=0.482,P<0.01)和双眼视力(r=0.492,P<0.01)有相关性.精神心理健康维度中,选项类别阈值分别为-2.83、0.03、2.80,PSR/PSI为0.88/2.68,PCA第一成分未解释方差特征值为2.79,匹配度为-0.34,所有条目DIF值均小于1;该维度得分与好眼视力(r=0.425,P<0.01)和双眼视力(r=0.426,P<0.01)有相关性.上述所有条目infit和outfit值均介于0.50~1.50之间.结论:基于Rasch分析研制的白内障PROs条目库覆盖了视觉相关活动受限、视觉症状和精神心理健康3个方面,全面地反应了白内障PROs的内涵,且条目简明易懂,临床可操作性好,具有较好的测量特性.     

Evaluation of the Chinese Adult Strabismus-20 （CAS-20） questionnaire using Rasch analysis

ObjectiveTo further refine the Chinese Adult Strabismus-20 （CAS-20） health-related quality of life（HRQOL） questionnaire using Rasch analysis. MethodsIn this cross-sectional study, the CAS-20 questionnaire was independently completed by 246 adult strabismus patients. Based on the score for each item, Rasch analysis was performed on the original CAS-20 using the following aspects： dimensionality, response order, local dependence, infit and outfit analysis, differential item function, subject targeting and confirmatory dimensionality. ResultsThe original CAS-20 was divided into 4 subscales, which were labeled ″self-perception″, ″interaction″, ″reading function″, and ″general function″. Response ordering was appropriate for all of the 4 subscales. As a result of infit and outfit analysis, 3 items were removed, one each from ″self-perception″, ″reading function″, and ″general function″. No significant differential item function was found for sex or age. Compared with the ability of the patients and item difficulty, the 3 subscales matched well except for ″reading function″. ConclusionThe original CAS-20 was reduced to 17 items, and divided into 4 subscales, which were ″self-perception″, ″interaction″, ″reading function″, and ″general function″. Subject response choices saved 5 test options. The refined CAS-20 may prove to be more responsive to HRQOL changes in adult strabismus patients.     

Visual Functioning Questionnaire: reevaluation of psychometric properties for a group of working-age adults.

PURPOSE: The Visual Functioning Questionnaire (VFQ-25) is one of the most widely used measures of vision-related quality of life. However, the questionnaire does not meet some psychometric quality criteria. The objectives of this study were first to obtain the factor structure of the VFQ-25, and second, to obtain interval scales by Rasch analysis. METHODS: The questionnaire was administered to 129 visually impaired adults (mean age 42.1 years; range 21 to 67 years). First, the items of the VFQ-25 were subjected to an exploratory factor analysis with Promax rotation. Next, we performed a separate Rasch analysis on each factor. We examined step thresholds and goodness of fit statistics of the items. Finally, we examined differential item functioning. RESULTS: Factor analysis indicated four factors: Near Activities, Distance Activities and Mobility, Mental Health and Dependency, and Pain and Discomfort. They accounted for 46.37% of the total variance. Most items showed some degree of disordering. After collapsing response categories, all items showed ordered thresholds. The Near Activities domain showed excellent fit, whereas the Distance Activities and Mobility domain, the Mental Health and Dependency domain, and the Pain and Discomfort domain had an unsatisfactory fit. There were two items showing uniform differential item functioning. CONCLUSIONS: The four-factor structure of the VFQ-25 largely confirms the structure of the questionnaire. However, the results of this study suggest that modifications of the original VFQ-25 structure are necessary.     

Validation of a Visual Function and Quality of Life Instrument in an Urban Indian Population with Uncorrected Refractive Error Using Rasch Analysis

Purpose: To develop and validate a patient-reported outcome measure of refractive error for persons living in developing countries.

Methods: A 21-item visual function questionnaire was developed from existing instruments through pilot testing in 51 urban Indian adults with refractive error. This was then administered to 400 adults aged 18 to 45 in Delhi, India. Rasch analysis was performed to determine item fit, differential item functioning (DIF), targeting of the instrument to the study population, and instrument precision.

Results: The removal of 5 items from the instrument resulted in better fit to the Rasch model. Reducing the number of possible responses from five to four further improved fit. Analysis of the person-item map including the Fisher information function demonstrated acceptable targeting of the instrument to this population. The person separation index was good (2.03), demonstrating ability to differentiate between 3 strata of respondents.

Conclusions: Revisions to existing instruments to measure visual function in persons with refractive error resulted in an instrument that conformed to the Rasch model. Identifying activities that are more difficult to perform with refractive error in this setting might further improve the instrument. The 16-item instrument was able to differentiate among levels of impairment due to uncorrected refractive error and could be used to assess refractive programs in similar settings.     

中文版低视力者生活质量量表的 Rasch分析

目的：通过Rasch分析评估中文版低视力者生活质量量表（CLVQOL）,优化提炼该量表。方法：回顾 性系列病例研究。收集2017年1-12月在温州医科大学附属眼视光医院低视力门诊就诊的低视力患 者189例,对其进行CLVQOL问卷调查。患者的年龄为（40.9±20.2）岁,男/女比例为1.6∶1。根据 每一量表的每一条目得分情况使用Winsteps 3.72.2软件的等级模式进行Rasch分析,分析条目及答案 的心理计量特征。分析的项目内容分别为：分解维度、选项排序、局部独立性、适合度分析、项目 差别功能和项目适中性分析。结果：CLVQOL由4个维度组成。各维度选项之间存在互相包含现象, 且第一特征根均在2左右,单维性检验尚在可接受范围内。选项排序发现选项2和4与其相邻选项分 离不够清晰。同一维度内条目间具有较好的独立性。第四维度Q24的适合均方为1.55,不适合均方 为1.58,超过了0.60～1.40的标准范围。按性别分析4个维度的项目功能差异,Q24在性别间差异大 于5。项目与个体匹配不是很好,除了第三维度项目平均分高于个体平均得分外,其他维度项目平 均得分均低于个体平均得分。同时,各维度对个体的测量信息也较低。结论：CLVQOL具有良好的 信效度,通过Rasch分析表明其量表选项应根据我国社会经济背景及低视力人群生活需求进行重新 设计优化,使量表更适用于中国低视力人群。     

The Activities of Daily Vision Scale for cataract surgery outcomes: re-evaluating validity with Rasch analysis

PURPOSE: The Activities of Daily Vision Scale (ADVS) has been extensively validated by traditional methodology. In the current study, Rasch analysis was used to explore further the validity of the ADVS and to determine whether improvements could be made. METHODS: Forty-three patients with cataract underwent visual acuity (VA) and contrast sensitivity (CS) testing and completed the ADVS. The data were Rasch analyzed and the value of response scale and item reduction explored. A shortened version and the original ADVS were tested for criterion validity by determining correlations with VA and CS. RESULTS: The ADVS data contained abnormally distributed items and items with ceiling effects and empty response categories. Therefore, items benefited from shortening the response scale, the optimum length being three responses. There was poor targeting of item difficulty to patient ability, because many patients with cataract were sufficiently able that they had no difficulty with many activities. Items were eliminated if the task was too easy or did not fit with the overall concept of visual disability determined by the Rasch model. A reduced ADVS version was established that had adequate precision, equivalent criterion validity, and improved targeting of item difficulty to patient ability, but this version was still not ideal. CONCLUSIONS: Despite careful traditional validation, the ADVS data contained inadequacies exposed by Rasch analysis. Through Rasch scaling, particularly with response scale reduction, the ADVS can be improved, but additional questions seem to be needed to suit the more able, including patients undergoing second eye cataract surgery. There remains a need to develop Rasch-scaled measures of visual disability for use in ophthalmic outcomes research.     

Assessment of the impact of vision impairment

PURPOSE: To describe the psychometric characteristics of the Impact of Vision Impairment (IVI) Profile and evaluate its validity and reliability over time and between different forms of administration. METHODS: The IVI is a 32-item questionnaire developed to measure the impact of vision impairment on restriction of participation in daily activities in five domains of functioning. Each item is rated on a six-level scale from "no difficulty" to "can't do because of vision." The IVI was administered by trained interviewers to 115 people with impaired vision (visual acuity less than 6/12 or visual field deficit) who attended the Royal Victorian Eye and Ear Hospital, a vision rehabilitation agency, or a self-help group for people with impaired vision. Data were also collected on demographic characteristics of participants, cause of vision impairment, and distance and near vision. General health status was assessed with the Short Form-12 (SF-12) of the Physical and Mental Health Summary Scales. A subset of participants completed the IVI twice, either 1 to 2 weeks apart or by different forms of administration (different interviewers or self). RESULTS: Internal consistency of total and domain average IVI scores was high (alpha = 0.80-0.96) and sequential elimination of items did not affect consistency. Total and domain average IVI scores correlated moderately with both near and distance vision (r = 0.21-0.31) but did not correlate with physical or general health or comorbidity. Total and domain average IVI scores correlated most closely with global measures of restriction of participation (r = 0.44-0.82). Principal-components analysis confirmed that all IVI items contribute to one underlying theme and tended to confirm two of the five domains: emotional reaction to vision loss and mobility. The first three components explained 43%, 8%, and 6% of the variation in the data. Guttman split-half reliability coefficients between different forms of administration and over time ranged from 0.73 to 0.94 for domain and total IVI scores. Mean absolute difference for domain and total scores between administrations was less than 1 step for all domains and the total score. CONCLUSIONS: This study provides support that the IVI has sufficient internal and construct validity to measure the effect of vision impairment on restriction of participation in daily activities. The IVI demonstrates acceptable reliability over a short period and yields consistent results between interviewers. The IVI can also be self-administered with assurance that the results will be comparable to those that would have been obtained by a trained interviewer. Therefore, the psychometric characteristics of the IVI support its use in assessment of the vision rehabilitation needs of people with impaired vision. Its stability over time indicates that it has potential to evaluate outcomes of intervention.     

The development of the LV Prasad-Functional Vision Questionnaire: a measure of functional vision performance of visually impaired children

PURPOSE: To develop a reliable and valid questionnaire (the LV Prasad-Functional Vision Questionnaire, LVP-FVQ) to assess self-reported functional vision problems of visually impaired school children. METHODS: The LVP-FVQ consisting of 19 items was administered verbally to 78 visually impaired Indian school children aged 8 to 18 years. Responses for each item were rated on a 5-point scale. A Rasch analysis of the ordinal difficulty ratings was used to estimate interval measures of perceived visual ability for functional vision performance. RESULTS: Content validity of the LVP-FVQ was shown by the good separation index (3.75) and high reliability scores (0.93) for the item parameters. Construct validity was shown with good model fit statistics. Criterion validity of the LVP-FVQ was shown by good discrimination among subjects who answered "seeing much worse" versus "as well as"; "seeing much worse" versus "as well as/a little worse" and "seeing much worse" versus "a little worse," compared with their normal-sighted friends. The task that required the least visual ability was "walking alone in the corridor at school"; the task that required the most was "reading a textbook at arm's length." The estimated person measures of visual ability were linear with logarithm of the minimum angle of resolution (logMAR) acuity and the binocular high contrast distance visual acuity accounted for 32.6% of the variability in the person measure. CONCLUSIONS: The LVP-FVQ is a reliable, valid, and simple questionnaire that can be used to measure functional vision in visually impaired children in developing countries such as India.     

Impact of cataract surgery on quality of life in patients with early age-related macular degeneration.

PURPOSE: To investigate if cataract surgery improves overall and specific areas of quality of life (QoL) in patients with early age-related macular degeneration (AMD) using the impact of vision impairment (IVI) questionnaire. METHODS: Patients with visually significant cataract and early AMD, who were being considered for cataract surgery in the study eye, were recruited. Eligible patients were randomized to either "early surgery" or "standard surgery" (standard cataract surgery waiting time of 6 months) groups. The IVI, sociodemographic, and clinical data were collected. Rasch analysis was used to estimate QoL person measures at baseline and follow-up. The data were analyzed using repeated measures ANOVA. Effect sizes were calculated using Cohen's d coefficient. RESULTS: Fifty six patients (mean age = 78.5 years and visual acuity = 6/15) had one eye randomly allocated to either the early surgery (n = 29) or standard surgery (n = 27) groups. At follow-up, significant interaction effects were found for the overall IVI score [F(1,54) = 17.7; p < 0.001], the emotional well-being [F(1,54) = 13.4; p = 0.001], mobility and independence [F(1,54) = 13.4; p = 0.001], and reading and accessing information subscales [F(1,54) = 13.1; p = 0.001]. The standard surgery group systematically recorded worse scores at 6 months on all QoL measures whereas the early surgery group recorded significant gains (p < 0.001; Cohen's d = 0.66 to 0.91) on all of them. Visual acuity in the study eye significantly improved in the early surgery group only (Cohen's d = 1.1; p < 0.05) and improvement in log MAR lines read was identified as the single independent predictor of enhanced QoL explaining between 26 and 34% of the variance in the IVI scores. CONCLUSIONS: Cataract surgery is justified in patients with early AMD. It brings significant improvements in visual acuity, aspects of daily living, and overall QoL.     

Psychometric properties of the Veterans Affairs Low-Vision Visual Functioning Questionnaire

PURPOSE: To describe psychometric properties of a self-report questionnaire, the Veterans Affairs (VA) Low-Vision Visual Functioning Questionnaire (LV VFQ-48), which was designed to measure the difficulty visually impaired persons have performing daily activities and to evaluate low-vision outcomes. METHODS: The VA LV VFQ-48 was administered by telephone interview to subjects with visual acuity ranging from near normal to total blindness at five sites in the VA and private sector. Rasch analysis with the Andrich rating scale model was applied to difficulty ratings from 367 subjects, to evaluate measurement properties of the instrument. RESULTS: High intercenter correlations for item measure estimates (intraclass correlation coefficient [ICC]=0.97) justified pooling the data from these sites. The person measure fit statistics (mean square residuals) confirm that the data fit the assumptions of the model. The item measure fit statistics indicate that responses to 19% of the items were confounded by factors other than visual ability. The separation reliabilities for pooled data (0.94 for persons and 0.98 for items) demonstrate that the estimated measures discriminate persons and items well along the visual ability dimension. ICCs for test-retest data (0.98 for items and 0.84 for persons) confirm temporal stability. Subjects used the rating categories in the same way at all five centers. Ratings of slight and moderate difficulty were used interchangeably, suggesting that the instrument could be modified to a 4-point scale including not difficult, slightly/moderately difficult, extremely difficult, and impossible. Fifty additional subjects were administered the questionnaire with a 4-point scale to confirm that the scale was used in the same way when there were four rather than five difficulty ratings. CONCLUSIONS: The VA LV VFQ-48 is valid and reliable and has the range and precision necessary to measure visual ability of low-vision patients with moderate to severe vision loss across diverse clinical settings.     

Evaluation of the NEI visual functioning questionnaire as an interval measure of visual ability in low vision

The National Eye Institute developed a visual functioning questionnaire (NEI-VFQ) designed to assess health-related quality of life of patients with visual impairments. The developers of the NEI-VFQ distributed the original 52 items into 13 different domains. The recommended method for scoring the NEI-VFQ is to linearly transform the sum of the ordinal ratings to each item within each domain to produce 13 scores. The major shortcoming of this scoring method is that sums of ordinal numbers do not necessarily generate valid measurement scales. However, Rasch models can be used to estimate interval measurement scales from ordinal responses to items. We administered 27 items from the 52-item NEI-VFQ to 341 patients with low vision. Rasch analysis was used to estimate the 'visual ability' required by each item for a particular response (item measures) and to estimate the 'visual ability' of each patient (person measures). The validity of the model was evaluated by examining the distributions of residuals for item and person measures. We observed that the 17 items we tested from the NEI-VFQ that require difficulty ratings produce a valid interval scale for low-vision patients. The estimated person measures of visual ability are linear with log MAR acuity. The ten items that require frequency or level of agreement ratings do not work together to produce a valid interval scale. Rather, these items appear to be confounded by other variables distributed in the patient sample (e.g. psychological state). The visual ability scale estimated from the 17 NEI-VFQ items is proportional to the visual ability scales estimated from two earlier studies that also elicited difficulty ratings from low-vision patients.     

中文版IND-VFQ-33在白内障人群中的应用与评价

目的研制中文版印度视功能量表（IND-VFQ-CN-33）,评价其在中国白内障人群中的测量特性,并初步分析白内障患者术前生活质量的影响因素。方法横断面调查研究。对IND-VFQ-33量表进行标准的翻译、回译和跨文化调试后,选取在温州医科大学附属眼视光医院确诊的白内障住院患者293例进行调查,其中45例患者用于评估2名调查者信度。通过Cronbach′s α系数分析量表的内部一致性;Pearson相关分析评估评定者间信度;内容效度指数评估内容效度;探索性因子分析评估结构效度,评价量表的适用性、项目区分度及信度、效度。通过独立样本t检验分析不同性别、年龄、文化程度条件下生活质量的差异,并通过单因素方差分析不同双眼远视力情况下生活质量的差异。结果中文版IND-VFQ-CN-33项目区分度好。内部一致性和评定者间信度较高,总表的Cronbach′s α系数为0.93。量表水平内容效度指数为0.84;结构效度的探索性因子分析提取出8个公因子,累积方差贡献率为67.62%。男性患者的心理评估子表得分高（t=-3.27,P＜0.05）,文盲患者的视功能子表（t=-3.03,P＜0.05）和心理评估子表（t=-3.45,P＜0.05）得分高。单因素方差分析发现不同双眼远视力组间差异均有统计学意义（F=3.66~24.37,P＜0.05）。结论IND-VFQ-CN-33在中国白内障术前人群中适用性好,具有较优的测量特性,可用于中国白内障术前人群的生活质量评估研究。白内障男性患者的心理方面生活质量下降较女性更加显著,文盲患者的视功能和心理方面生活质量下降较非文盲患者更加显著。     

中文版儿童间歇性外斜视生存质量量表的Rasch分析

目的通过Rasch分析提炼和优化中文版儿童间歇性外斜视量表（CIXTQs）,以更好地评估中国间歇性外斜视儿童和家长的生存质量状况。方法横断面研究。在2016年6-8月期间收集5~17岁间歇性外斜视儿童青少年211例,平均年龄（9.7±3.0）岁。其中5~7岁54例,8~17岁157例。分别按要求对儿童和家长采用CIXTQs进行调查,分为5~7岁儿童、8~17岁儿童、家长代理和家长问卷4个量表。根据每一量表的每一条目得分情况使用Winsteps 3.72.3软件的等级模式进行Rasch分析,分析条目及答案的心理计量特征。各量表分析的项目包括分解维度、选项排序、局部独立性、适合度分析、项目适中性分析、最终确定维度等。结果选项排序发现5~17岁儿童青少年量表的选项均为3个,分别是“从来没有”、“有时”、“总是”,家长代理量表和家长问卷量表保留的选项排序和原量表相同,为5个。家长问卷量表仍保留3个维度,分别为功能维度、社会心理维度和手术维度;项目适合度分析发现需要删减家长问卷量表的功能维度中的条目1,社会心理维度中的条目5;删减条目后发现家长问卷量表中的手术维度的个体分离指数较差（＜1.5）。项目适中性分析发现各量表项目难度和研究对象个体能力之间的匹配情况均很好。结论提炼和优化后的CIXTQs将能更明确地反映间歇性外斜视对儿童青少年及其家长生存质量影响的因素,更敏感地评估间歇性外斜视儿童及其家长的生存质量状况。