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Purpose The Caregiver's Congenital Glaucoma QoL (CarCGQoL) questionnaire was proposed as a measure of QoL of caregivers with children with primary congenital glaucoma (PCG). Support for its psychometric properties among other diagnostic groups is required for scores to be interpreted in the same manner across groups. Therefore we investigated the measurement properties and cross-diagnostic validity of the CarCGQoL questionnaire among caregivers of children with congenital cataract, retinopathy of prematurity (ROP), and blinding corneal disorders. Methods Eight hundred ninety-one caregivers (mean age, 28.3 years; 76% mothers) of children with congenital cataract (n = 407), ROP (n = 272), and blinding corneal disorders (n = 212) completed the CarCGQoL questionnaire. Rasch analysis was used to investigate the psychometric properties. Unidimensionality (by principal components analysis of residuals, PCA) was examined for each group and for pooled sample. Differential item functioning (DIF) was investigated to explore whether bias in responses to the questionnaire existed for certain subgroups as compared to the reference group (PCG). Results Across groups, six items necessitated removal because of misfit (two common and four uncommon), after which three different versions of the questionnaire emerged. Measurement precision was adequate for each group and for the pooled sample (0.80). Unidimensionality was observed, albeit with some DIF. Regardless of the level of QoL, caregivers in the pooled sample were more likely to endorse two items reflecting ability to face child's disease, and interest to pursue leisure activity, as compared with caregivers of children with PCG. Conclusions Care must be taken when data from the CarCGQoL questionnaire from different pediatric ocular conditions are pooled, given the presence of DIF between the reference group (PCG) and the pooled sample. Translational relevance When evaluating the impact of interventions on the caregiver's QoL using the CarCGQoL questionnaire in a pooled sample of pediatric ocular conditions, cross-diagnostic DIF must be taken into account.

Purpose Little is known about quality of life (QoL) and life satisfaction (LS) of treated primary congenital glaucoma (PCG) patients in adulthood. The purpose of this study was to assess the QoL and LS and their predictors among young adults treated for PCG during early childhood. Design Cross-sectional study. Participants Eighty-two participants with PCG (mean age, 22.5 years; standard deviation [SD], 4.6); 52% were male; 94% bilateral) recruited at L V Prasad Eye Institute. Methods Participants were asked to complete the 26-item World Health Organization Quality of Life–BREF (WHOQOL-BREF) questionnaire (items related to satisfaction with general health, physical, psychological, social relations, and environmental aspects) and the 5-item Satisfaction with Life Scale (SWLS) in the clinic visit. Clinical data including visual acuity (VA) and visual fields (VFs) were collated from medical records. Rasch analysis was used to optimize the psychometric properties, with higher scores indicating a higher degree of QoL and LS, for both the questionnaires. Linear regression models were used to examine associations between overall QoL and LS (in separate models), and sociodemographic and clinical variables. Main Outcome Measures The QoL and LS were measured using Rasch-transformed scores from the WHOQOL-BREF questionnaire and SWLS, respectively. Results Response rate was 93%. The overall mean (SD) Rasch-scaled scores for QoL were 0.93 (1.11) and 0.87 (1.32) for environment domain and 0.41 (1.56) logits for LS. Better QoL was significantly related to rural residence and higher education in both univariable and multivariable analyses and explained 13% variance. Higher LS was significantly related to marital status, unilateral affliction, and higher education in univariable analyses. However, multivariable regression analysis showed that only marital status was independently associated with higher LS and explained 8.8% of variance. Clinical and treatment variables (VF, surgical interventions, medications) were not independent predictors of QoL/LS. Conclusions Our results suggest that QoL and LS of treated patients with PCG during adult life are generally good and appear to be driven by factors other than clinical indices. Educational achievement appears to be linked to better QoL and LS, and clinicians should emphasize the importance and need for education in the continued care of these patients.

SIGNIFICANCE: The Indian translated and culturally adapted version of the vision-related activity limitation (VRAL) item bank is a validated instrument to assess the difficulty in performing daily activities by cataract patients and can also be used to capture self-reported changes in ability to perform daily activities after cataract surgery. PURPOSE: The purpose of this study was to document (a) translation, cross-cultural adaptation of VRAL item bank into an Indian language, and (b) its validation using Rasch analysis in a South Indian cataract population. METHODS: At the first stage, a translated Indian version of VRAL item bank was produced using recommended procedures. At the second stage, Rasch analysis was performed to investigate its psychometric properties in 787 cataract patients (mean age, 58.2 years; mean ± SD visual acuity [logMAR], 1.19 ± 0.96 at baseline in eye for surgery) including comparison with the original version. RESULTS: Post-translation equivalence of meaning was achieved, but some English phrases required cross-cultural adaptation. Subsequently, all items were appropriate for the Indian culture, and VRAL item bank demonstrated excellent measurement precision (7.39). Dimensionality assessment suggested that VRAL construct may contain other dimensions such as self-care and visual search, and mobility. Self-care and visual search formed a unidimensional measure but was highly correlated with main VRAL dimension, and the removal of its items weakened precision of the main VRAL dimension measurement. Taken together, evidence favored retaining self-care and visual search items in a larger VRAL item bank. Mobility subscale lacked adequate measurement precision, so it was not examined further; again, items were retained in VRAL scale because they strengthened its measurement properties. Majority of items (99%) did not demonstrate notable differential item functioning (>1.0 logit) by presenting visual acuity (median, 0.20 logMAR) in the better-seeing eye. CONCLUSIONS: Items in the translated Indian VRAL item bank measure the same construct as the English version and fulfilled the psychometric requirements for use in cataract patients. Refereed/Peer-reviewed

Purpose Provide item calibrations estimated for the Impact of Vision Impairment (IVI) questionnaire by pooling data from several studies of people with vision impairment (VI) representing a variety of countries and causes of VI. Methods Eight data sets from six principal investigators representing responses to IVI items from 2867 VI patients were pooled for analysis. Eligible patients were 18 years or older and from Australia, India, and the United States. Rasch analysis, using the Andrich Rating Scale Model (Winsteps version 3.65), was performed on preintervention IVI responses to estimate item and person measures, reliability coefficients, and response category thresholds. Differential item functioning (DIF) analysis and analysis of variance (ANOVA) were used to examine the effects different data sets and covariates on item estimates. Results Patient age range was 18 to 103 years (median 62 years); 55% were male. Visual acuity ranged from 20/20 to no light perception and primary diagnosis was macular degeneration in 29% of patients. Item measure estimates showed good separation reliability (R2 = 0.99). DIF magnitude did not preclude use of all IVI-28 data. ANOVA showed VA (P < 0.001) and gender (P < 0.002) were predictors of visual ability. Conclusions Analysis from pooled data support the provision of calibrated IVI item measures for researchers and clinicians to use, thus better enabling direct comparisons of patients with VI. Translational Relevance Validity testing of the IVI show that we can combine disparate data sets of patient responses to calibrate item measures and response category thresholds, and provide to others for use in comparing patients across clinical trials and on an individual basis.

PURPOSE: To evaluate the health-related quality of life (HRQoL) of children operated for primary congenital glaucoma (PCG) using the Kidscreen-27 questionnaire. METHODS: A total of 121 children (mean age, 11.8 years; SD, 2.8 years; 51% males) with unilateral or bilateral PCG who underwent glaucoma surgery in infancy (mean duration since surgery, 10.2 years; [SD] 4.2 years) by a single surgeon at a tertiary eye care centre were administered the Kidscreen-27 questionnaire (self-or interviewer administered in a face-to-face interview) during their routine follow-up visit. We investigated the measurement properties of Kidscreen-27 questionnaire using Rasch analysis and generated interval-level estimates of HRQoL. The main outcome measure was HRQoL (i.e., Rasch-derived Kidscreen score). Multivariable linear regression analyses assessed the influence of socio-demographic and clinical variables on the HRQoL of children with PCG. RESULTS: Majority (83%) of the children had bilateral PCG and congenital type of the disease (79%). Mean presenting acuity (logMAR) in the better eye was 0.32 (SD, 0.36; median, 0.18). Rasch analysis of Kidscreen-27 questionnaire indicated need for minor modifications following which a psychometrically robust unidimensional 23-item Kidscreen questionnaire emerged. In multivariable model, age of the child was independently associated with a 32% (β = −0.24 [95% CI, −0.11, −0.36]) increase in the HRQoL score. CONCLUSIONS: Despite undergoing successful glaucoma surgery, children with PCG reported reduced HRQoL. Younger children with PCG are more likely to experience this lowered HRQoL and ophthalmologists will need to be alert to this. Efforts must be made to improve the HRQoL of children with PCG.

Purpose We developed and validated an instrument to measure the quality of life (QoL) of caregivers of children with primary congenital glaucoma (PCG): the Caregiver's Congenital Glaucoma Quality of Life (CarCGQoL) questionnaire. Methods A total of 70 caregivers of children with PCG under follow-up at a tertiary eye care center in India participated in a series of focus groups, and pre- and pilot testing phases in the development of the 45-item CarCGQoL questionnaire. Subsequently, this instrument was administered to 111 caregivers of children with PCG awaiting glaucoma surgery. Response to each item was rated on a four-category scale. Rasch analysis was used to validate the instrument's psychometric properties, such as unidimensionality (by principal components analysis [PCA] of residuals), item fit to model, measurement precision (by person separation [PS]), response category performance, differential item functioning (DIF), and targeting of items to participant's QoL. Results Categories required reorganization resulting in a shortened rating scale of 3 categories. The instrument showed misfit to the Rasch model and lacked unidimensionality. Deleting 15 items (obtained through PCA of residuals) restored unidimensionality, but additional items misfit, necessitating item reduction. In addition, 2 items showed DIF and were deleted. Finally, a 20-item CarCGQoL instrument showed good fit and unidimensionality. Targeting was good (0.69 logits) and PS was 2.51, indicating good measurement precision. Conclusions We have developed a psychometrically robust 20-item caregiver derived questionnaire, the CarCGQoL, that is a valid and reliable measure of QoL of caregivers of children with PCG. Given its brevity, it is quick and easy to administer in the clinic, and has potential for use as an outcome measure in clinical trials of treatment of PCG.

Background The Patient-Health Questionnaire (PHQ-9) is a widely used screening instrument for depression. Recently, its properties as a measure were investigated using Rasch analysis in an Australian population with visual impairment (VI) and it was demonstrated to possess excellent measurement properties, but the response scale required shortening (modified PHQ-9). However, further validation was recommended to substantiate its use with the growing population of VI. Therefore, we aimed to use Rasch analysis to evaluate the measurement properties of the modified PHQ-9 in an Indian population with VI. Methods 303 patients with VI (mean age 40.2 years; 71% male) referred to Vision Rehabilitation Centres were administered the PHQ-9 by trained interviewer. Rasch analysis was used to investigate the psychometric properties of the modified PHQ-9. Results Rasch analysis showed good fit to the model, no misfitting items and an acceptable person separation reliability (0.82). Dimensionality testing supported combining 9 items to create a total score. Targeting was sub-optimal (−1.30 logits); more difficult items are needed. One item (‘trouble falling asleep’) showed notable differential item functioning, DIF (1.18 logits) by duration of VI. Limitations The generalisability of these results might be restricted to patients with VI presenting to a tertiary eye care centre. Conclusions Except for DIF, the performance of the modified PHQ-9 is consistent with that of the original, albeit in a different cultural context (Indian population with VI). Clinicians/researchers can readily use the modified PHQ-9 without formal training in Rasch procedures given the provision of ready-to-use spreadsheets that convert raw to Rasch-scaled scores. However the conversions will apply only if the sample being tested is similar to that of the present study.

To validate the Indian-translated Impact of Vision Impairment for Children (IVI_C), a vision-related quality of life (VRQoL) instrument, and to investigate the effect of sociodemographic and ocular characteristics on VRQoL.The 24-item IVI_C was administered face to face to 221 children with vision impairment (VI) (mean age, 12.6 years; male, 68%) referred to the Vision Rehabilitation Centres. Rasch analysis was used to investigate the IVI_C for key indices such as measurement precision as measured by person separation (minimum recommended value, 2.0), unidimensionality (i.e., whether all the items contribute toward measurement of a single underlying construct as assessed by item fit and principal component analysis of residuals), targeting of items to participants' VRQoL (i.e., matching of item difficulty to participant ability; ideal targeting,1.0 logits). Univariate analysis was performed to determine if the person scores of IVI_C were significantly different across participant subgroups stratified by sociodemographic and ocular characteristics, including the severity of VI.The IVI_C showed misfit to the model and lacked unidimensionality. Principal component analysis confirmed the presence of an additional construct, mobility, but it did not possess adequate person separation when assessed individually. Deleting the mobility-related items restored unidimensionality, but additional items misfit, necessitating item reduction. Finally, a 17-item IVI_C possessed good measurement precision (person separation, 2.04), was unidimensional (albeit not purely), and consisted of items that fit the Rasch model and were well targeted to the participants' VRQoL (targeting 0.76 logits). There was no statistically significant difference in the VRQoL across subgroups stratified by age, sex, type of school, cause of VI, duration of vision loss, and severity of VI (p0.05 for all).The revised 17-item IVI_C is shorter and has better psychometric properties than the original version in school-aged children with VI in India, and the responses are unrelated to sociodemographic and clinical variables. Although it has the potential for use in cross-sectional and outcomes research in children with VI, caution should be exercised while interpreting the 17-item IVI_C scores given the presence of slight multidimensionality.

PURPOSE: To explore the psychometric properties of the revised Olweus Bully/Victim Questionnaire (OBVQ) in children with visual impairment (VI) using Rasch analysis. METHODS: One hundred fifty Indian children with VI between 8 and 16 years (mean age, 11.6 years; 69% male; mean acuity in the better eye of 0.80 logMAR [Snellen, 20/126]) were administered the revised OBVQ. The 40-item revised OBVQ was developed to assess victimization (i.e., being bullied) and bullying (bullying others) in normally sighted schoolchildren. Only 16 items are used for Rasch analysis and are divided into two parts: I (victimization, eight items) and II (bullying others, eight items). Separate Rasch analysis was conducted for both parts, and the psychometric properties investigated included behavior of rating scale, extent to which the items measured a single construct (unidimensionality by fit statistics and principal component analysis [PCA] of residuals); ability to discriminate among participants' victimization and bullying behaviors (measurement precision as assessed by person separation reliability [PSR] minimum recommended value, 0.80); and targeting of items to participants' victimization and bullying. RESULTS: Response categories were misused for both parts I and II, which required repair before further analysis. Measurement precision was inadequate for both parts (PSR, 0.64 for part I and 0.19 for part II), indicating poor discriminatory ability. All items fit the Rasch model well in part I, indicating unidimensionality that was further confirmed using PCA of residuals. However, an item misfit in part II that required deletion following which the remaining items fit and PCA of residuals also supported unidimensionality. Targeting was -0.58 logits for part I, indicating that the items were matched well with the participants' victimization. By comparison, targeting was suboptimal for part II (-1.97 logits). CONCLUSIONS: In its current state, the revised OBVQ is not a valid psychometric instrument to assess victimization and bullying among children with VI. Language: en

Previous Rasch analysis of the Andhra Pradesh Eye Disease Study-Visual Function Questionnaire (APEDS-VFQ) lacked comprehensiveness, specifically, dimensionality (whether it measures single/multiple constructs). Therefore, using the Rasch model this study provides a detailed assessment of psychometric properties of the APEDS-VFQ.A total of 351 visually impaired adults (mean age, 43.3 years) were verbally administered the APEDS-VFQ. Rasch analysis was used to assess the psychometric properties of the instrument.Participants could distinguish only three categories of difficulty, so response categories were reduced from five to three. A single item ("reading small prints in newspaper/magazines", infit mean square 1.54) misfit the model. The overall pattern of fit statistics for item and person measures suggested that the underlying construct (visual ability) is not unidimensional. When the items were grouped into subsets based on functional requirements (resolution, contrast sensitivity, illumination and peripheral vision) and separate person measures were estimated for each of these domains, the first principal component contained the visual ability and accounted for 72% of the variance. Item measure distributions could be divided into 18 strata, and item-separation reliability was 0.99. Person measures could be divided into three statistically distinct strata and the person-separation reliability was 0.81.The APEDS-VFQ is a precise measure of visual ability in visually impaired adults in India. Similar to other visual function questionnaires developed for the Western population, our results demonstrate that visual ability is a two-factor composite latent variable; one dimension heavily influences reading and the other most heavily influences peripheral vision (mobility).

To examine the psychometric characteristics of the World Health Organization Quality of Life instrument—modified Indian version (modified WHOQOL) and its subscales in adults with visual impairment (VI) using Rasch analysis. Cross-sectional data were of people aged ≥40 years with VI (n = 1,333) who responded to the modified WHOQOL in the Andhra Pradesh Eye Disease Study, India. Rasch analysis was used to explore the instrument and its subscales for key indices such as measurement precision by person separation reliability, PSR (i.e., discrimination between strata of participants’ health-related QOL [HRQOL], recommended minimum value 0.8), unidimensionality (i.e., measurement of a single construct), and targeting (i.e., matching of item difficulty to participants’ HRQOL). Rasch-guided iterative approach including category re-organization to enable threshold ordering and item deletion to overcome multidimensionality resulted in a unidimensional 9-item WHOQOL and a 6-item level of independence (LOI) subscale with adequate PSR (0.81 and 0.82, respectively). Targeting was sub-optimal for both (−1.58 logits for WHOQOL and −2.55 logits for the subscale). Remaining subscales were dysfunctional. The WHOQOL and LOI subscale can be improved and shortened, and the Rasch-revised versions are likely to assess the HROQL of VI patients best because of their brevity, reliability, and unidimensionality.

Aim To investigate the psychometric properties of the three scales (general functioning, psychosocial impact, visual symptoms) of the Indian vision function questionnaire (INDeVFQ) using the Rasch measurement model. Methods 236 visually impaired patients referred to vision rehabilitation centres were administered the 33item INDeVFQ. Rasch analysis was used to investigate the scales for the following properties: precision by person separation (ie, discrimination between strata of patient ability, recommended minimum value 2.0), unidimensionality (ie, measurement of a single construct) and targeting (ie, matching of item difficulty to patient ability). Results Only the general functioning scale possessed adequate measurement precision (person separation 3.49). However, it lacked unidimensionality as some items did not contribute towards the measurement of a single construct indicating a secondary dimension. This comprised seven mobility items, which formed a separate valid subscale with good targeting (� 0.57 logits). Deleting these items restored unidimensionality but a misfitting item required removal. Following this the 13 items fit and were visual functioning related. However, targeting was suboptimal (� 1.13 logits). Conclusions The general functioning scale of the INDeVFQ consists of two separate unidimensional constructs: visual functioning and mobility. Both these Rasch scaled versions with good psychometric properties are effective tools for the assessment of visually impaired patients in India.

Purpose: Many questionnaires for the measurement of visual impairment exist. One, the Houston Vision Assessment Test (HVAT), takes a different approach: the patient is asked to rate overall impairment and the proportion attributed to vision, then through multiplication the visual and non-visual (physical) impairments are calculated. The purpose of this study was to determine whether the scores derived from this approach can be considered to be measures. Methods: The participants were 193 cataract patients awaiting surgery (mean age 74.1 ± 9.8 years, 54 per cent female and 53.6 per cent were awaiting first eye surgery), who self-administered the HVAT, which consists of 10 questions, whereby impairment on each activity and the proportion attributable to vision is rated. Therefore, total, visual and physical impairments are calculated. For each question, multiplying the impairment (five response categories) by the proportion due to eyesight (five categories) gives 10 possible levels of visual impairment. Assessment of the multiplicative rating scales included frequency of category use and hierarchical ordering of response categories using category thresholds. Summary statistics of Rasch analysis were generated for the rating scale and overall questionnaire performance. Results: In the multiplicative scale, higher response categories were under-utilised and thresholds were disordered, indicating that the categories did not function as intended. Some of the dysfunction arose from disordered thresholds in the ‘proportion due to eyesight scale’, but repairing this gave little improvement to the multiplicative scale. The ill-defined nature of the disordered categories precluded further repair by combining categories. Measurement precision, as indicated by person separation reliability, was poor (0.70). Conclusion: Rasch analysis demonstrated that the categories of the multiplied rating scale of the HVAT were not ordered, as the user would expect; this precludes measurement. This provides evidence against the use of multiplicative rating scales in quality-of-life questionnaires. It would be better to use a single rating scale for each construct of interest.

Purpose: To determine whether the eight subscales of the Refractive Status and Vision Profile (RSVP) questionnaire provide valid measurement. Methods: Two hundred patients, recruited from a refractive surgery clinic and general optometric practice, self-administered the 42-item RSVP questionnaire. Psychometric properties investigated included measurement of a single construct (unidimensionality), item fit to construct, measurement precision (represented by person separation), targeting of item difficulty to patient’s quality of life (QOL), and differential item functioning. Results: Only two subscales (“concern” and “driving”) showed adequate person separation, indicating that they could discriminate patients’ QOL. However, both demonstrated poor targeting (7.02 logits for “driving” and 1.11 logits for “concern”). One-third of items in each subscale suffered from differential item functioning. Conclusions: None of the RSVP subscales are valid for assessment of QOL in patients with refractive error, thereby indicating the RSVP should be considered as a single questionnaire without subscales.

Purpose We assess parent-child agreement regarding child's health-related quality of life (HRQoL) in children operated for congenital glaucoma (CG). Methods A total of 121 children aged 8 to 18 years (mean age, 11.8 years) operated for CG (mean duration since surgery, 10.2 years) and their parents (mean age, 36.5 years) completed the child and parent versions of the Kidscreen-27 questionnaire, respectively. Psychometric properties of Kidscreen-27 were assessed using Rasch analysis, and child-parent agreement regarding child's HRQoL was investigated using the Bland-Altman limits of agreement (LoA) method. Results Minor modifications in the rating scale and deletion of few misfitting items resulted in a psychometrically robust Kidscreen-23 questionnaire. Average parental HRQoL score was higher than the child's own ratings, with a significant difference between their scores (mean ± standard deviation [SD] difference = 0.53 ± 2.58 logits, P = 0.02; lower LoA [95% CI], -4.52 [-5.31 to -3.72] and upper LoA [95% CI], 5.58 [4.79-6.38]). The range of child-parent agreement was wide and bidirectional, with parents tending to underestimate and overestimate their child's HRQoL. Younger children and girls showed greater discordance in their HRQoL with parental reports than adolescents and boys, respectively. Conclusions Discordance between CG child's self-report of HRQoL and parent's report indicate that both groups perceive the broader impact of living with CG very differently. Translational relevance The HRQoL as reported by the child with CG and by his/her parent should be viewed as being complementary, rather than interchangeable. Both assessments should be taken into account in clinical practice and research studies.

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. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Purpose To examine the psychometric properties of the Visual Activities Questionnaire (VAQ) and each of its subscales in a modern cataract population using Rasch analysis and if flawed, to revise the VAQ and create a valid measure that maximizes its measurement properties. Setting Flinders Eye Centre, Flinders Medical Centre, Adelaide, Australia. Methods Patients with cataract in 1 or both eyes drawn from the surgical waiting list were mailed the 33-item VAQ for self-administration. The following were examined for the entire questionnaire and each subscale: whether items measured a single construct (unidimensionality), the behavior of response categories, the ability to differentiate between patients' visual abilities (person separation), matching of item difficulty to participant ability (targeting), and whether items function similarly across subgroups of participants (differential item functioning [DIF]). Results The VAQ was completed by 561 patients. Response categories were used as intended. The VAQ discriminated the visual ability of the population (person separation, 4.88) but had suboptimum targeting, misfitting items, significant multidimensionality, DIF, and 4 dysfunctional subscales. Elimination of items causing multidimensionality resulted in a reduced 13-item VAQ that met all validity criteria for satisfactory instrument performance. Only 1 valid subscale (peripheral vision) could be preserved in the 13-item VAQ. Conclusions The VAQ in its native form was multidimensional and contained subscales with poor psychometric properties. The revised unidimensional 13-item VAQ was more appropriate for application in cataract outcomes assessment. Ideally, more items should be included to improve the targeting of item difficulty to more able cataract patients.

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

Purpose: The 5-item Cataract Symptom Score (CSS) was developed using classical test theory to determine appropriate timing for cataract surgery, its outcomes, and whether the symptoms included bother cataract patients. The purpose of this study was to investigate the psychometric properties of the 5-item CSS using Rasch analysis. Methods: Responses from 113 patients awaiting cataract surgery to the 5-item CSS (bothered by double or distorted vision, glare or halos, blurry vision, colors looking different and worsening of vision) were subjected to Rasch analysis. The use of response categories (threshold order), ability of CSS to discriminate between participants' severity of symptoms (person separation, recommended minimum value 2.0), matching of item difficulty to severity of symptoms (targeting), and ability of items to measure a single construct (unidimensionality) were investigated. Results: Participants used the response categories as intended. However person separation (1.74) was inadequate, suggest...

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. (Optom Vis Sci 2009;86:E826–E835)

PurPose: The Adaptation to Age-related Vision Loss (AVL) scale was developed to measure the adjustment of older adults who are adapting to late-life vision loss. The purpose of this study was to assess whether the AVL scale satisfies the Rasch model in a cataract population. Methods: The 24-item AVL scale (18 negatively and 6 positively coded) was mailed to 436 cataract patients for self-administration whilst they were on the waiting list for cataract surgery at the Flinders Eye Centre, Adelaide, South Australia. Rasch analysis was performed to determine whether the items were measuring a single construct (unidimensionality) as examined with fit statistics and principal components analysis (PCA) of the residuals. The ability of the scale to distinguish between the levels of adaptation of the participants (person separation) was investigated, with a value ≥ 2.0 established as the minimum acceptable. results: The AVL scale was unable to differentiate sufficiently between participants’ levels of adaptation, indicating poor person separation. One item did not fit the construct, causing misfit. Furthermore, the five positively worded items did not appear either to measure the same construct as other items, resulting in lack of unidimensionality evidenced by PCA. Following the deletion of these items, the AVL scale was one-dimensional but a single item continued to misfit, so it had to be deleted, resulting in an 18-item AVL scale. Even so, the discriminating abilities of the scale continued to be poor. ConClusions: The AVL scale is not an appropriate measure of adaptation to vision loss in a cataract population. (J Optom 2009;2:142-147 ©2009 Spanish Council of Optometry)

We determined if the Impact of Vision Impairment (IVI) is a valid questionnaire to measure the vision-related quality of life (VRQoL) in keratoconus patients, and investigated if the VRQoL varied with disease severity in this sample.WE RECRUITED 160 CONSECUTIVE BILATERAL KERATOCONUS PATIENTS (MEAN AGE 23.3 YEARS, 63% MALE) FROM AN INDIAN TERTIARY EYE CARE CENTER. PARTICIPANTS UNDERWENT A CLINICAL EXAMINATION AND COMPLETED THE IVI. PARTICIPANTS WERE DIVIDED INTO THREE GROUPS BASED ON THE AVERAGE OF THE STEEP KERATOMETRY (K) READINGS: mild (average Sim K45 diopters [D]), moderate (average Sim K 45-52 D), and severe (average Sim K52 D). Rasch analysis was used to validate the IVI and the VRQoL scores thus obtained were compared across the disease groups.THE MAJORITY (63%) OF PATIENTS HAD SEVERE, WHILE THE REMAINDER (37%) HAD MODERATE KERATOCONUS. RASCH ANALYSIS DEMONSTRATED THE VALIDITY OF THE IVI TO ASSESS VRQOL THROUGH TWO SUBSCALES: vision-specific functioning (VF) and emotional well-being (EWB). There was no significant difference in VF (mean change -0.16, P = 0.55) and EWB scores (mean change -0.32, P = 0.23) between moderate and severe keratoconus groups.The revised IVI subscales have interval-level measurement properties, which support their suitability to measure VRQoL in this keratoconus sample. Patients with moderate or severe keratoconus had similar, but higher VRQoL scores as assessed by the revised IVI subscales, indicating lack of impact of the disease on their VRQoL. However, this does not exclude the possibility of finding an impact in other populations.

Purpose The L. V. Prasad-Functional Vision Questionnaire (LVP-FVQ) was developed using Rasch analysis to assess self-reported difficulties in performing daily tasks in school children with visual impairment (VI) in India. However, the LVP-FVQ has psychometric problems of inadequate measurement precision and lack of detailed assessment of dimensionality. Furthermore, items pertaining to use of technology are lacking. The aim of this study was to present the development and validation of the second version of LVP-FVQ (LVP-FVQ II). Methods Development of LVP-FVQ II involved extracting items from other similar questionnaires (albeit developed for Western populations) and focus group discussions of children with VI and their parents that resulted in a 32-item pilot questionnaire. Overall, six items from the LVP-FVQ were retained. The questionnaire underwent pilot testing in 25 such children, following which a 27-item LVP-FVQ II emerged, and this was administered to 150 children with VI. Response to each item was rated on a three-category scale. Rasch analysis was used to validate the LVP-FVQ II. Results Rating scale was used by participants as was intended to. Four mobility-related items required deletion, as these did not contribute toward measurement of a single construct, indicating a secondary dimension. Deletion of the four items resulted in the 23-item unidimensional LVP-FVQ II, with good measurement precision, effective targeting of item difficulty to participant ability, and lack of notable differential item functioning. The LVP-FVQ II has high reliability, indicating that it is effectively able to discriminate between visual disability of school children in India, and is valid across age, gender, duration of VI, and location of residence. Conclusions Given the superior measurement properties and the interval-level scores, the LVP-FVQ II appears to offer advantages over LVP-FVQ in assessment of difficulties in performing daily tasks in this population. It can be adapted for use in other developing countries.

PURPOSE To evaluate the impact of glaucoma on visual functioning in Indians. METHODS Patients attending the glaucoma service who had undergone a comprehensive glaucoma evaluation were recruited. Better mean deviation (MD, using Humphrey Field Analyzer program 24-2) between two eyes was used to classify participants into mild, moderate, and severe visual field (VF) loss groups. Participants were administered the Glaucoma Quality of Life-15 (GQL-15) questionnaire. Rasch analysis was used to validate the GQL-15 and its four subscales. Linear regression was used to determine associations between GQL-15 scores and VF loss after adjusting for sociodemographic variables. RESULTS A total of 198 patients (mean age ± SD, 59.8 ± 12.3 years; 67% male) were recruited. Participants with severe VF loss (39%) followed by mild loss (35%) comprised the largest group. Rasch analysis resulted in a 10-item reliable and valid questionnaire: the Glaucoma Activity Limitation-10 (GAL-10). Although a single subscale, "peripheral vision," met requirements of the Rasch model, it could not be preserved in the GAL-10. In multivariate analyses, the middle-income group (compared with higher income) and severe VF-loss (compared with mild VF-loss) participants reported significantly poorer functioning on GAL-10 ([β = 0.84; 95% confidence interval (CI), 0.16-1.52; P = 0.02] and [β = 1.19; 95% CI, 0.61-1.78; P < 0.000], respectively). None of these associations were, however, clinically significant. CONCLUSIONS Glaucoma patients in India, especially those with severe VF loss, face significant challenges in performing daily tasks and in mobility. It is important to prevent progression such that activity limitation is minimized in glaucoma patients.

A critical component that influences the measurement properties of a patient-reported outcome (PRO) instrument is the rating scale. Yet, there is a lack of general consensus regarding optimal rating scale format, including aspects of question structure, the number and the labels of response categories. This study aims to explore the characteristics of rating scales that function well and those that do not, and thereby develop guidelines for formulating rating scales. Methods: Seventeen existing PROs designed to measure vision-related quality of life dimensions were mailed for self-administration, in sets of 10, to patients who were on a waiting list for cataract extraction. These PROs included questions with ratings of difficulty, frequency, severity, and global ratings. Using Rasch analysis, performance of rating scales were assessed by examining hierarchical ordering (indicating categories are distinct from each other and follow a logical transition from lower to higher value), evenness (indicating relative utilization of categories), and range (indicating coverage of the attribute by the rating scale). Results: The rating scales with complicated question format, a large number of response categories, or unlabelled categories, tended to be dysfunctional. Rating scales with five or fewer response categories tended to be functional. Most of the rating scales measuring difficulty performed well. The rating scales measuring frequency and severity demonstrated hierarchical ordering but the categories lacked even utilization. Conclusion: Developers of PRO instruments should use a simple question format, fewer (four to five) and labelled response categories., This work was supported in part by National Health and Medical Research Council (Canberra, Australia) Centre of Clinical Research Excellence Grant 264620. Konrad Pesudovs and Ecosse Lamoureux are supported by National Health and Medical Research Council (Canberra, Australia) Career Development Awards 426765 and 529902, respectively.

PURPOSE Both the long form visual functioning scale (LFVFS(39)) and visual functioning scale (VFS) are measures of visual functioning (VF) that represent the Rasch-scaled versions of the NEI-VFQ(39) and the Indian vision function questionnaire (IND-VFQ), respectively. The objectives of this study were to investigate if the 15-item LFVFS(39) and 13-item VFS of the IND-VFQ meet the assumptions of the Rasch model and measure the same construct, VF, in an Indian visually impaired (VI) population. METHODS Data from 120 VI adults administered both instruments concurrently, were fitted to the Rasch measurement model to demonstrate that each instrument satisfies the assumptions of the model (including unidimensionality by principal components analysis); and both instruments can be cocalibrated onto a single underlying continuum of VF. RESULTS Both instruments required category reorganization for optimal rating scale functioning and possessed similar measurement precision (person separation = 2.76). Separate analysis of each instrument (eigenvalues, 2.3 and 1.9 for LFVFS(39) and VFS of IND-VFQ, respectively) and the pooled 28-item analyses (eigenvalue, 2.8) satisfied the assumptions of the Rasch model, including unidimensionality. Furthermore, all items fit in the separate and pooled analyses. Separate item and person measures for each instrument correlated strongly with estimates from the pooled data (r > 0.9 for all, P < 0.0001). CONCLUSIONS; Both the LFVFS(39) and VFS of the IND-VFQ measure the same construct, VF, and with equal measurement precision in an Indian VI population. Both instruments can be calibrated onto a single metric, thereby, enabling a comparison of their measurement range of VF.

Purpose: To investigate the effect of rating scale designs (question formats and response categories) on item difficulty calibrations and assess the impact that rating scale differences have on overall vision-related activity limitation (VRAL) scores. Methods: Sixteen existing patient-reported outcome instruments (PROs) suitable for cataract assessment, with different rating scales, were self-administered by patients on a cataract surgery waiting list. A total of 226 VRAL items from these PROs in their native rating scales were included in an item bank and calibrated using Rasch analysis. Fifteen item/content areas (e.g., reading newspapers) appearing in at least three different PROs were identified. Within each content area, item calibrations were compared and their range calculated. Similarly, five PROs having at least three items in common with the Visual Function (VF-14) were compared in terms of average item measures. Results: A total of 614 patients (mean age ± SD, 74.1 ± 9.4 years) participated. Items with the same content varied in their calibration by as much as two logits; “reading the small print” had the largest range (1.99 logits) followed by “watching TV” (1.60). Compared with the VF-14 (0.00 logits), the rating scale of the Visual Disability Assessment (1.13 logits) produced the most difficult items and the Cataract Symptom Scale (0.24 logits) produced the least difficult items. The VRAL item bank was suboptimally targeted to the ability level of the participants (2.00 logits). Conclusions: Rating scale designs have a significant effect on item calibrations. Therefore, constructing item banks from existing items in their native formats carries risks to face validity and transmission of problems inherent in existing instruments, such as poor targeting. Refereed/Peer-reviewed

Aim The Visual Disability Assessment (VDA), a questionnaire for measuring the impact of cataract on visual functioning, was developed using classical test theory. Since this approach is limited, our aim was to further investigate the psychometric properties of the VDA using Rasch analysis. Methods 613 patients from the Flinders Medical Centre cataract surgery self-administered the VDA. Psychometric properties investigated for the overall VDA and each subscale included: measurement of a single construct (unidimensionality), item fit to the construct, reliable discrimination between strata of patient ability (person separation) and targeting of item difficulty to person ability. Results The VDA discriminated five strata of patient ability. However, seven mobility items constituted a second dimension and formed a valid separate scale. Sequestration of these items resulted in a unidimensional 11-item measure of activity limitation. Both the mobility and activity limitation scales had acceptable person separation and neither contained misfitting items. Targeting was suboptimal for mobility (−2.12 logits) but good for activity limitation (−0.72). The subscales also satisfied the requirements of the Rasch measurement model. Conclusions The Rasch-scaled VDA effectively measures two separate constructs: mobility and activity limitation (with two subscales). Its good psychometric properties make it suitable for measuring cataract surgery outcomes.

PURPOSE: To determine which version of the Visual Function Index-14 (VF-14) most precisely measured cataract surgery outcomes, rescale the VF-14 using Rasch analysis, and create a short-form version for comparison. SETTING: Flinders Medical Centre, Adelaide, South Australia, Australia. METHODS: In this cohort study incorporating questionnaire development, participants were drawn from the cataract surgery waiting list at Flinders Medical Centre. There were 2 cohorts: a preoperative cohort used for questionnaire development and an outcomes cohort. All patients had cataract surgery by phacoemulsification with intraocular lens implantation. Rasch analysis was used to refine the VF-14 into valid long-form (VF-11R) and short-form (VF-8R) versions. The ability of 8 versions (original; 2 proposed versions; 5 previously proposed versions) of the VF-14 to discriminate cataract surgery outcomes was compared with that of the standard VF-14 using the relative precision method. RESULTS: The preoperative cohort comprised 210 patients and the outcomes cohort, 51 patients. Large gains in visual functioning occurred with cataract surgery, and these were detectable with all versions of the VF-14. The largest gain in precision, 125% (relative precision. 2.25), occurred for VF-8R. Short forms that were not Rasch scaled showed gains in precision, from 23% to 80%. The VF-8R also showed the largest gains in precision in 2 subgroups: with ocular comorbidity (relative precision, 2.14) and without ocular comorbidity (relative precision, 2.48). CONCLUSIONS: Results show an unequivocal advantage to using Rasch-scaled scores for assessing cataract surgery outcomes. The 8-item, Rasch-scaled VF-8R appears ideally suited for measuring cataract surgery outcomes given its high precision and short test time. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Purpose To determine, by using Rasch analysis, whether the McMonnies questionnaire possesses the properties of a measure and whether screening for dry eye syndromes (DESs) can be enhanced by using different scoring approaches. Methods The questionnaire was self-administered by 43 female Sjogren syndrome patients (>45 years) recruited from a specialized rheumatology clinic and 140 age-matched control subjects. Data were scaled by using Rasch analysis and were assessed for response category behavior and ability to reliably discriminate between severity of the participant's dry eye symptoms (i.e., person separation reliability; minimum acceptable value, 0.80). Standard summary statistics of screening performance were calculated for raw and Rasch-scaled scores from receiver-operating characteristic analysis including area under the curve (AUC). Best predictors (i.e., questions) from a discriminant analysis were used to calculate a discriminant function for both Rasch-scaled and raw scores. Results Response categories were not used as intended, necessitating a collapse of categories. Person separation reliability was inadequate (0.75). A Rasch-scaled discriminant cutoff score of -2.29 logits from seven items provided an AUC of 0.99 with 95% sensitivity. However, discriminant raw score from modification in the scoring of a question (e.g., use of medications), used as one rather than multiple questions, provided an AUC (0.97) that was not significantly different (z = 1.11, P = 0.27), with 98% sensitivity, and required only two questions. Conclusions In this population, the McMonnies questionnaire does not function as a measure. However, various scoring methods can be used to efficiently screen for DES.

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.

Purpose. To investigate the psychometric properties of the Visual Function (VF) and Quality of Life (QOL) questionnaires, using the Rasch measurement model. Methods. Four hundred eighty-nine patients with cataract awaiting surgery, drawn from the surgical waiting list of the Flinders Medical Centre, Adelaide, South Australia, were mailed the VF and QOL questionnaires for self-administration. Rasch analysis was undertaken to assess the following properties: measurement of a single construct (i.e., unidimensionality by fit statistics and principal components analysis), discrimination between strata of participant ability (person separation, recommended minimum value 2.0), targeting of item difficulty to participant ability, and differential item functioning (DIF, whether items function similarly for different subgroups and notable DIF defined as >1.0 logit). Results. The VF questionnaire fit the Rasch model showing good metric properties, including unidimensionality, and was free of notable DIF. The QOL questionnaire showed inadequate person separation, two misfitting items and significant multidimensionality (Eigenvalue of 2.3 for the first contrast), suggesting the presence of a separate subscale, self-care, but this was not valid because of inadequate person separation. Deleting these contrasting items from the QOL questionnaire removed multidimensionality and item misfit but did not improve person separation, indicating that it could not effectively discriminate between the participant’s QOL. Both VF and QOL questionnaires demonstrated poor targeting (−2.22 and −3.26 logits, respectively), indicating that items were too easy and participants had higher QOL than that the items allowed for. Three items in the QOL questionnaire demonstrated notable DIF by age and systemic comorbidity. None of the subscales functioned optimally. Conclusions. The QOL questionnaire is not a valid measure of QOL. However, the VF questionnaire is a reliable and valid measure of visual disability in patients with cataract, and although targeting was suboptimal in a developed country, it may be optimal in a developing country as was originally intended.

Aim: Previous psychometric evaluation of the Cataract Symptom Scale (CSS) focused on classic assessments of reliability and validity. The aim was to investigate the psychometric properties of the CSS using the Rasch measurement model. Methods: 243 patients drawn from the Flinders Eye Centre cataract surgery waiting-list self-administered the CSS. Rasch analysis was used to investigate the following properties of the CSS: measurement a single construct (unidimensionality), discrimination between strata of patient ability (person separation) and targeting of item difficulty to person ability. Results: The CSS discriminated between four strata of patients. However, some items did not contribute towards measurement of a single construct, indicating a secondary dimension. This comprised three mobility items, which formed a separate valid subscale. Elimination of these items resulted in the CSS being a unidimensional measure. However, further item deletion was required, as symptoms items did not measure the same construct. The resultant nine-item measure was unidimensional. Conclusions: The CSS consists of two separate unidimensional constructs: mobility and visual disability. The reduced nine-item measure has good psychometric properties and is unidimensional. The CSS is essentially a measure of visual disability, and not cataract symptoms as it is claimed to be.

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 Quality of life and Vision Function Questionnaire (QOL-VFQ) was developed using classical test theory to assess outcomes of cataract surgery. The aim of this study was to examine the psychometric properties of this questionnaire using Rasch analysis in a cataract population.The 17-item QOL-VFQ was self-administered to 389 patients waiting to undergo cataract surgery. The QOL-VFQ and its five subscales were assessed for fit to the Rasch model. Rasch analysis was used to estimate interval level measures of "visual ability" from ordinal scores for the QOL-VFQ and its five subscales. Unidimensionality, item fit, response category performance, and targeting of items to patients were assessed.The QOL-VFQ and its five subscales showed ordered category thresholds. Despite removal of two misfitting items the person separation reliability was high and the QOL-VFQ could distinguish among three strata of patient ability. However, there was suboptimal targeting of patient ability to item difficulty as most of the patients had higher levels of visual functioning. None of the subscales demonstrated acceptable psychometric properties.These results support the good overall functioning of the QOL-VFQ in patients with cataract. However, adding more items, that suit the more able patients including those who are awaiting cataract surgery in the fellow eye, will help improve the targeting.

The Distance Vision Scale (DVS) is a self-assessment of visual acuity (VA). Like VA testing in which letter reading becomes progressively difficult through the test, DVS questions have a hierarchy of difficulty (Guttman scale). The aims were to determine whether the DVS fulfills Guttman scaling criteria and to test the relationship between DVS score and VA in a cataract population.Responses of 113 participants to the DVS were subjected to Guttman analysis. Standard criteria of scalability were evaluated that included the coefficient of reproducibility (CR), minimal marginal reproducibility (MMR), and coefficient of scalability (CS). The relationship between total item score and binocular visual acuity was determined.Five participants were excluded because of missing data. Regularity in the banding pattern of the scalogram of the 108 participants was suggestive of a deterministic Guttman scale. Analyses showed that DVS satisfies the criteria for classification as a valid unidimensional and cumulative scale, as CS (0.93), CR (0.99), and MMR (0.85) values fall within the desired range. The statistically significant correlation between the total item score and binocular VA was 0.24.The DVS fits the Guttman scale, supporting the deterministic model underlying the scale. It correlates poorly with VA, suggesting it taps aspects of visual performance and other issues beyond high-contrast VA. The DVS could be used as an outcome measure to evaluate change over time and could be used to set achievable treatment objectives because of its hierarchical properties.

PURPOSE: To assess the psychometric properties of the Cataract TyPE Specification (Spec) questionnaire using the Rasch model. SETTING: Flinders Medical Centre, Adelaide, Australia. METHODS: The 12-item Cataract TyPE Spec questionnaire was self-administered to patients drawn from the cataract surgery waiting list. The questionnaire and its 5 subscales were assessed for fit to the Rasch model. Response category performance, item-fit targeting, unidimensionality (using principal components analysis), and differential item functioning were assessed. A shortened version (11 items) was tested for criterion validity by determining correlation with a global rating of vision question. RESULTS: Two hundred ninety-four patients responded to the questionnaire. The response categories for each question functioned as intended. Person-separation reliability was high (0.90). Deletion of 1 misfitting item (nighttime driving) improved overall model fit. The principal components analysis of the residuals demonstrated unidimensionality for the 11-item Cataract TyPE Spec and 2 subscales. However, items were targeted to a less able population. Only 2 subscales (near vision and glare) were valid. There was a good statistically significant correlation between the Likert-scored global rating of vision and the Rasch-scaled Cataract TyPE Spec score (r Z 0.66, P

To evaluate the change in visual functioning (VF) using the L. V. Prasad-Functional Vision Questionnaire II (LVP-FVQ II) following multidisciplinary low vision rehabilitation (LVR) services in children with low vision (LV).Children with LV referred for the first time to the Centre for Sight Enhancement were administered the LVP-FVQ II at baseline and at 3 to 4 months' follow-up to assess the outcomes of LVR. Participants' responses to the LVP-FVQ II at baseline and follow-up were transformed into interval-level estimates of VF using Rasch analysis. Cohen's d values (effect size) were used to estimate the magnitude of change in VF.A total of 183 participants completed the rehabilitation (mean age, 11.9 years; male, 57%). More than one-half of the participants had retinal disorders (55%) and most were moderately visually impaired (20/60-20/200, 76.5%). Using the LVP-FVQ II, significant improvement in VF after rehabilitation was recorded (P0.0001) and the increase in VF (SD) was 1.20 (1.82) logits. Using Cohen's d, the magnitude of the improvement in LVR intervention at follow-up was found to be 0.75, indicating nearly large treatment effect.Ours is the first study to provide strong evidence that LVR services result in nearly large and significant improvements in the overall VF in children with LV, regardless of the cause of LV. These results should encourage eye care professionals to refer children with LV to LVR services. Further investigation is needed to determine if the improvement in VF can be sustained over a longer duration (4 months).

Purpose To evaluate the psychometric properties of the Adult Strabismus-20 (AS-20)- a health-related quality of life (HRQoL) questionnaire in adults with strabismus, and if flawed, to revise the AS-20 and its subscales creating valid measurement scales. Methods 584 adults (meanage, 27.5 years) with strabismus were recruited from an outpatient clinic at a South Indian tertiary eye care centre and were administered the AS-20 questionnaire.The AS-20 was translated and back translated into two Indian languages. The AS-20 and its two 10-item subscales – ‘psychosocial’ and ‘function’were assessed separately for fit to the Rasch model, including an assessment of the rating scale, unidimensionality (by principal components analysis), measurement precision by person separation reliability, PSR, targeting, and differential item functioning (DIF; notable > 1.0 logits). Results Response categories were not used as intended, thereby, required re-organization and reducing their number from 5 to 3. The AS-20 had adequate measurement precision (PSR = 0.87) but lacked unidimensionality; however, deletion of the six multi-dimensionality causing items and an additional three misfitting items resulted in 11-item unidimensional questionnaire (AS-11). Two items failed to satisfy the model expectations in the ‘psychosocial’ subscale and were deleted – resulting in an 8-item unidimensional scale with adequate PSR (0.81) and targeting (0.23 logits). One item misfit in the ‘function’ subscale and was deleted—resulting in a 9 item Rasch-revised unidimensional subscale with acceptable PSR (0.80) and targeting (0.97 logits).None of the items displayed notable DIF by age, gender and level of education. Conclusions The AS-11 and its two Rasch-revised subscales – 8-item psychosocial and 9-item function subscale may be more appropriate than the original AS-20 and its two 10-item subscales for use as unidimensional measures of HRQoL in adults with strabismus in India. Further work is required to establish the validity of the revised rating scale.

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 (

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.

BACKGROUND: Depression and anxiety are two common normal responses to a chronic disease such as glaucoma. This study analysed the measurement properties of the depression screening instrument - Patient Health Questionnaire-9 (PHQ-9) using Rasch analysis to determine if it can be used as a measure. METHODS: In this hospital-based cross-sectional study, the PHQ-9 was administered to primary glaucoma adults attending a glaucoma clinic of a tertiary eye care centre, South India. All patients underwent a comprehensive clinical evaluation. Patient demographics and sub-type of glaucoma were abstracted from the medical record. Rasch analysis was used to investigate the following properties of the PHQ-9: behaviour of the response categories, measurement precision (assessed using person separation reliability, PSR; minimum recommended value 0.80), unidimensionality (assessed using item fit [0.7-1.3] and principal components analysis of residuals), and targeting. RESULTS: 198 patients (mean age ± standard deviation = 59.83±12.34 years; 67% male) were included. The native PHQ-9 did not fit the Rasch model. The response categories showed disordered thresholds which became ordered after category reorganization. Measurement precision was below acceptable limits (0.62) and targeting was sub-optimal (-1.27 logits). Four items misfit that were deleted iteratively following which a set of five items fit the Rasch model. However measurement precision failed to improve and targeting worsened further (-1.62 logits). CONCLUSIONS: The PHQ-9, in its present form, provides suboptimal assessment of depression in patients with glaucoma in India. Therefore, there is a need to develop a new depression instrument for our glaucoma population. A superior strategy would be to use the item bank for depression but this will also need to be validated in glaucoma patients before deciding its utility.

Purpose We evaluated the utility values (UVs), using the time trade off (TTO) technique, associated with primary glaucoma and varying degrees of visual field (VF) loss. Methods In this cross-sectional study, 198 adults (mean age, 59.8 years) with primary glaucoma were recruited from the glaucoma clinic of a tertiary center in Hyderabad, South India. Each patient underwent comprehensive glaucoma evaluation, and completed the utility (TTO) and Glaucoma Quality of Life-15 questionnaires (Rasch version, Glaucoma Activity Limitation [GAL]-10). Better mean deviation (MD, using Humphrey Field Analyzer program 24-2) between two eyes was used to classify participants into mild, moderate, and severe VF loss groups. Utilities (range, 0.0-1.0) derived by TTO technique (lifetime traded against perfect vision) and interval level Rasch scores of GAL-10 were used for analyses. Results Mean UV was 0.81 (95% confidence interval [CI], 0.78-0.84); that is, a decrease in quality of life (QoL) of 19%. Of the subjects, 59% were willing to trade lifetime in return of perfect vision; those willing to trade were significantly younger with poorer acuity in the worse-seeing eye. In univariate and multivariate analysis, severe VF loss in the worse eye was associated with lower UV (β = -0.108; 95% CI, -0.201 to -0.014; P = 0.02). Conclusions Our results show that primary glaucoma in adults causes substantial decrease in UVs (and QoL thereof), and is highly dependent on the severity of VF loss in the worse eye.

PURPOSE A multi-attribute utility instrument (MAUI) consists of a descriptive system in which the items and responses seek information about a concept of the universe of health-related quality of life (QoL), and responses to these items then are weighted and combined to produce the index. To our knowledge, the 6-item Vision and Quality of Life Index (VisQoL) is the only available vision-related MAUI, developed and validated in Australia, specifically for visually impaired (VI) populations. To our knowledge, the psychometric properties of the VisQoL have not yet been investigated in an Indian VI sample; this was the aim of our study. METHODS The Indian VisQoL was administered to 349 VI adults face-to-face by a trained interviewer at the Vision Rehabilitation Centres of a tertiary eye care facility, South India. Rasch analysis was used to assess the psychometric properties. RESULTS Rescoring was necessary for all except one item before ordered thresholds were obtained. All items fit the Rasch model and unidimensionality was confirmed. Person separation was acceptable (2.01), indicating that the instrument can discriminate among three strata of participants" vision-related QoL (VRQoL). The VisQoL items were targeted substantially to the participants" VRQoL (-0.69 logits). One item ("ability to have friendships") demonstrated large differential item functioning by work status; working participants reported the item to be more difficult (-1.13 logits) relative to other items when compared to the nonworking participants. CONCLUSIONS The 6-item Indian VisQoL satisfies unidimensional Rasch model expectations in VI patients. Disordering of response categories was evident; replication is required before a common rescoring option should be considered.

Purpose Previous Rasch analysis of the Activities of Daily Vision Scale (ADVS) did not address psychometric properties of its subscales or provide detailed assessment of dimensionality (whether the ADVS measures one or multiple constructs). This study was designed to examine these properties. Methods Two hundred thirty-two participants (mean age, 74.2 years) awaiting cataract surgery self-administered the ADVS. Rasch analysis was used to assess the ADVS and its five subscales for unidimensionality (by principal components analysis, [PCA]), precision by person separation (discrimination between strata of participant ability), and targeting (matching of item difficulty to participant ability). Adequate person separation (minimum acceptable value, 2.0) is the fundamental requirement for measurement. Results Only the near vision subscale had adequate measurement properties (person separation, 2.30). The entire ADVS showed a misfit to the Rasch model and lacked unidimensionality. PCA confirmed the presence of two additional traits-driving and glare disability-but neither possessed adequate person separation when assessed individually. Deleting these traits restored unidimensionality, but additional items misfit, necessitating item reduction. Finally, an eight-item ADVS-Near Vision Scale showed good fit and unidimensionality. Its contents were identical with the original near vision subscale. Targeting was suboptimal (2.30 logits). Conclusions Only one subscale, near vision, met the criteria for measurement. The revised eight-item ADVS-Near Vision subscale is a unidimensional measure of visual disability in cataract patients with mild visual disability. However, it is limited by measurement of near visual ability only. For more comprehensive measurement of visual disability, other questionnaires such as Catquest-9SF are preferable for cataract surgery outcomes assessment.

PURPOSE To determine the distribution of perceived visual ability for functional vision performance among persons with low vision in the Indian state of Andhra Pradesh. METHODS As part of a population-based epidemiologic study, the Andhra Pradesh Eye Disease Study (APEDS), a 16-item visual function questionnaire was designed and applied to 7363 persons older than 15 years, to record the levels of difficulty perceived by the subjects. Of these, 123 persons were found to have low vision. Rasch analysis was used to convert the ordinal difficulty ratings of these 123 persons into interval measures of perceived visual ability for functional vision. RESULTS Content validity of the questionnaire was demonstrated by good separation indices (3.17 and 5.44) and high reliability scores (0.91 and 0.97) for person and item parameters. Construct validity was shown with model fit statistics. Criterion validity of the questionnaire was shown by good discrimination among the general vision ratings. The functional situation that required the least visual ability was "reaching an object farther or closer than you thought"; the situation requiring the most visual ability was "recognizing small objects." Bivariate regression analysis determined that for every unit of logMAR visual acuity, perceived visual ability for functional vision decreased by 2.9 logit, which could explain 32% of the variability in the person measure. CONCLUSIONS The described assessment, across a range of visual problems, is a valid way to measure perceived ability for functional vision in persons with low vision. Perceived visual ability varies with every unit of logarithm of the minimum angle of resolution (logMAR) visual acuity.

PURPOSE. To determine the impact of visual impairment on functional vision of children in a rural population of south India. METHODS. A visual function questionnaire (LVP-VFQ) was administered to 1194 children aged 7 to 15 years identified through a systematic random sampling technique from 144 hamlets of Kariapatti in rural south India as part of a larger population-based project. Visual acuity estimations and clinical examinations for morbidity were performed in these 1194 children. A Rasch analysis was performed to validate the use of the instrument in this population. Bootstrap estimates (95% confidence intervals) of the regression coefficients were used to compare visual function scores between children with normal sight and children with uncorrected monocular and binocular visual impairment. RESULTS. The mean age of children was 10.3 ± 2.1 years. The reliability estimates were 0.82 for person ability and 0.88 for item difficulty parameters, according to the Rasch analysis. A separation index of 2.15 was obtained for person measures and 2.74 for item measures, and the mean square infit and outfit statistics were 1.03 (Z STn 0.1) and 0.99 (Z STD -0.1), respectively. Children with monocular visual impairment (bootstrap estimate [95%CI] -0.05 [-0.08 to -0.01]) and binocular visual impairment (bootstrap estimate [95%CI] -0.09 [-0.11 to -0.071) were more likely to have functional visual deficits than were normally sighted peers. CONCLUSIONS. Monocular or binocular visual impairment impacts on the functional vision of children in this rural population. Further studies are needed to determine the impact of treatment of visual impairment on functional vision in children of this population.