The Refractive Status and Vision Profile: Evaluation of psychometric properties and comparison of Rasch and summated Likert-scaling

Health-related quality of life measurements in children and adolescents with refractive errors: A scoping review

Background

Refractive errors, particularly myopia, are the leading visual disorders worldwide, significantly affecting the quality of life (QOL) even after correction. This scoping review focuses on health-related quality of life (HRQOL) measurements for children and adolescents with refractive errors.

Main text

We explored generic and disease-specific HRQOL tools, examining their content, psychometric properties, and the impact of various interventions on QOL. Two English databases-PubMed, Embase, and one Chinese database, CNKI, were searched for relevant studies published from January 2001 to October 2023. Inclusion criteria encompassed studies using standardized instruments to assess the QOL of children aged 0-18 with refractive errors. The review compares prevalent HRQOL measurements, analyzes children's refractive error assessments, and discusses intervention effects on patient QOL.

Conclusions

The study underlines the necessity of developing disease-specific QOL instruments for very young children and serves as a practical guide for researchers in this field. The findings advocate for a targeted approach in HRQOL assessment among the pediatric population, identifying critical gaps in current methodologies.

BCLA CLEAR Presbyopia: Evaluation and diagnosis

It is important to be able to measure the range of clear focus in clinical practice to advise on presbyopia correction techniques and to optimise the correction power. Both subjective and objective techniques are necessary: subjective techniques (such as patient reported outcome questionnaires and defocus curves) assess the impact of presbyopia on a patient and how the combination of residual objective accommodation and their natural DoF work for them; objective techniques (such as autorefraction, corneal topography and lens imaging) allow the clinician to understand how well a technique is working optically and whether it is the right choice or how adjustments can be made to optimise performance. Techniques to assess visual performance and adverse effects must be carefully conducted to gain a reliable end-point, considering the target size, contrast and illumination. Objective techniques are generally more reliable, can help to explain unexpected subjective results and imaging can be a powerful communication tool with patients. A clear diagnosis, excluding factors such as binocular vision issues or digital eye strain that can also cause similar symptoms, is critical for the patient to understand and adapt to presbyopia. Some corrective options are more permanent, such as implanted inlays / intraocular lenses or laser refractive surgery, so the optics can be trialled with contact lenses in advance (including differences between the eyes) to better communicate with the patient how the optics will work for them so they can make an informed choice.

Measurement of visual functioning following first and second eye cataract surgery using Vision-Related Activity Limitation Item Bank

PURPOSE

This study aims to compare visual functioning (VF) after first or second eye cataract surgery using the vision-related activity limitation (VRAL) item bank.

METHODS

This prospective, interventional study included 787 patients (mean age, 58.2 years) with cataract undergoing cataract surgery (first eye surgery with/out ocular comorbidity, second eye surgery with/out ocular comorbidity) at a tertiary eye care center, South India, who were administered the item bank pre- and at 6 weeks postoperatively to assess change in VF. Rasch analysis was used to estimate VF at both time points, and responsiveness to cataract surgery was calculated as effect size (ES) which was interpreted as small (≤ 0.2), moderate (0.3-0.7), and large (≥ 0.8).

RESULTS

Mean best-corrected logMAR VA in surgical eye improved significantly postoperatively compared to preoperative VA (0.20 ± 0.40 vs. 1.19 ± 0.96; P < 0.0001) across all groups. Patients reported significant and large improvements in VF postoperatively across all groups: largest ES for first eye surgery without comorbidity (1.87 [95% CI, 1.61, 2.13]) and smallest for second eye without ocular comorbidity (1.55 [95% CI, 1.22, 1.88]). Compared to patients undergoing second eye surgery, first eye surgery patients reported significantly lower VF preoperatively (-0.72 ± 2.39 vs. 0.17 ± 2.34 logits; P < 0.0001), and a larger change in VF postoperatively (3.71 ± 2.33 logits vs. 4.27 ± 2.83 vs.; P = 0.004).

CONCLUSIONS

Cataract surgery resulted in large and significant improvements in VF, regardless of ocular comorbidity and first or second eye surgery. The VRAL item bank is a useful tool to measure responsiveness to cataract surgery.

Content development for a new item-bank for measuring multifocal contact lens performance

BACKGROUND

Presbyopia is an age-related condition that causes a decreased ability to focus on nearby objects. Multifocal contact lenses are commonly used to address this issue. However, there seems to be a notable dissatisfaction among multifocal contact lens wearers. The absence of a reliable instrument to measure the patient's perspective, despite the widespread use of this method, highlights the need for further research in this area.

OBJECTIVE

The objective of this study is to develop an item-bank integrating all domains necessary to assess the patient's perspective on multifocal contact lens performance, offering a comprehensive measure. The item-bank will ensure a high level of content validity, be self-administered, and will initially be available in Spanish. The aim of this tool is to serve as a valuable resource for research and optometric clinics, facilitating the follow-up of patients with presbyopia who wear multifocal contact lenses or those who are newly starting to use them.

METHODOLOGY

The MCL-PRO item bank, followed a systematic and step-wise inductive approach to gather information, following the recommendations outlined in the COSMIN guidelines and similar studies. The process involved the following steps: (1) Literature review and relevant existing items identification (2) Social media review, (3) Semi-structured focus groups, (4) performing qualitative analysis, (5) refining and revising the items, and (6) generating the content of the item bank.

RESULTS

A total of 575 items were included in the item-bank hosted under 8 different domains that were found to be important for presbyopic population: visual symptoms (213), activity limitation (111), ocular symptoms (135), convenience (36), emotional well-being (33), general symptoms (16), cognitive issues (21) and economic issues (10).

CONCLUSION

The item-bank created has followed standardised methodology for its development and encloses all the aspects for MCL performance evaluation from patients perspective.

Ontario Cataract Quality Outcome Initiative: appropriateness and prioritization of cataract surgery

OBJECTIVE

To explore the utility of the Catquest 9SF visual function (VF) questionnaire along with visual acuity (VA) for determining appropriateness and priority for cataract surgery. To evaluate the feasibility of administering the Catquest-9SF in a clinical setting using web-based electronic data capture and interpretation.

DESIGN

Prospective multicentred interventional observational study.

PARTICIPANTS

Subjects undergoing sequential cataract surgery in both eyes at 4 sites in Ontario.

METHODS

We recorded best-corrected VA (BCVA) and VA with current correction (CCVA) in each eye and both eyes (OU) and Catquest-9SF responses on a tablet before and after cataract surgery. Linear regression models were employed to test for associations between VA and visual function (VF).

RESULTS

Preoperative BCVA and CCVA in the worse eye were significant predictors of change in VF (p = 0.006 and p = 0.008, respectively); subjects with worse VA had a greater improvement in VF after surgery. There was a significant association between improvement in VF and improvement in CCVA OU (p = 0.001). Fourteen of 151 subjects (9%) had no improvement or worse VF scores after surgery. Within this group, 10 of 14 subjects had a preoperative score ≤-3, which is suggestive of minimal visual disability. Within this subset, 4 of 14 subjects (2.6%) had a preoperative BCVA of 20/30 or better in their worse eye.

CONCLUSIONS

For patient groups with equal VA, the Catquest-9SF score can help determine priority for surgery. Web-based data capture and interpretation allow for efficient virtual assessments of VF. A BCVA in the worse eye of 20/30 or better combined with a Catquest-9SF score <-3 can be used as a guideline for lowest priority.

Catquest-9SF questionnaire: Validation in a Greek-speaking population using Rasch analysis

PURPOSE

The Catquest-9SF questionnaire is a tool measuring visual disability and vision-related limitation in patients' daily activities. The primary objective of this study was the validation of Catquest-9SF in a Greek-speaking cataract population.

METHODS

The questionnaire was translated into Greek and translated back into English. A pre-final Greek version was formed and tested by 10 Greek-English bilingual participants and by the translation team, and the final version was produced. Patients scheduled for cataract surgery completed the questionnaire preoperatively and postoperatively. Rasch analysis was performed for the assessment of the Catquest-9SF psychometric properties, including response category ordering, item fit statistics, principal components analysis, precision, differential item functioning and targeting for preoperative and postoperative data collectively.

RESULTS

A total of 100 (55 men, 45 women, mean age = 71.94±6.63) cataract patients completed the Greek version of Catquest-9SF questionnaire preoperatively and postoperatively. Rasch analysis showed a significant improvement in the median person Rasch score from -1.49 preoperatively to -4.71 logits postoperatively, while the effect size was 1.3. Unidimensionality was confirmed since infit and outfit mean square values varied between 0.66 and 1.37. Rasch analysis showed good precision and separation ability (Person Separation Index of 3.28, and Person Reliability of 0.92). Four response categories were found for all items. The item-person means difference was -1.83 logits. The difference between preoperative and postoperative Catquest-9SF logit score was positively correlated with preoperative Catquest-9SF logit score (coeff. = 0.798, p<0.0001) and negatively correlated with postoperative spherical equivalent (coeff. = -0.825, p = 0.011).

CONCLUSION

The Greek version of Catquest-9SF proved to be reliable, valid, unidimensional and responsive to changes after cataract surgery presenting good psychometric properties for cataract patients. Some postoperative mistargeting was found indicating that the tasks were easily performed by respondents after cataract surgery.

TRIAL REGISTRATION

NCT05323526 -retrospectively registered.

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

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

Patient-Reported Measures of the Effects of Vision Impairments and Low Vision Rehabilitation on Functioning in Daily Life

The quantification of vision impairments dates to the mid-nineteenth century with standardization of visual acuity and visual field measures in the eye clinic. Attempts to quantify the impact of vision impairments on patients' lives did not receive clinical attention until the close of the twentieth century. Although formal psychometric theories and measurement instruments were well developed and commonplace in educational testing, as well as in various areas in psychology and rehabilitation medicine, the late start applying them to clinical vision research created a vacuum that invited poorly developed and poorly functioning instruments and analytic methods. Although this research is still burdened with legacy instruments, mandates by regulatory agencies to include the patients' perspectives and preferences in the evaluation of clinical outcomes have stimulated the development and validation of self-report instruments grounded in modern psychometric theory and methods. Here I review the progress and accomplishments of applying modern psychometrics to clinical vision research. Expected final online publication date for the Annual Review of Vision Science, Volume 8 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Assessment of patient-reported outcome measures used in corneal transplantation: a systematic review

The aim of this study was to review all the articles that have implemented patient-reported outcome measures (PROMs) to evaluate the quality of life (QoL) in corneal transplantation and discuss quality assessments of the PROMs. An extensive literature review was undertaken to identify all the studies that used PROMs to assess the QoL in corneal transplantation. Non-original or review articles, articles on other subject area and articles on cost-effectiveness/utility without PROM data/results were excluded. Each PROM was assessed against the following criteria: content development (item identification and item selection), psychometric properties, validity, reliability, and responsiveness. 425 articles were identified of which 35 articles were included in the final review. PROMs in corneal transplantation were used to (a) evaluate the QoL after surgery, (b) compare the QoL scores between different surgical techniques and (c) determine the relationship between QoL and objective measures such as visual acuity, visual field and stereoacuity. A total of 17 PROMs were used to assess QoL in corneal transplantation. Whilst this search did not produce any PROMs that were specifically designed to assess corneal transplantation, most studies were found to have employed the National Eye Institute Visual Function Questionnaire 25 (NEI VFQ 25). The Visual Function Index 14 (VF 14) performed better in the present quality assessment criteria compared to other PROMs, however, the NEI VFQ 25 and the VF 14 PROMs were not specifically developed for corneal transplantation and therefore the QoL assessment made using these PROMs may be incomplete. As improvements in various forms of lamellar transplantation surgery techniques such as UT-DSAEK and FT-DSAEK have resulted in better visual outcomes, improved graft survival and reduced complications, a corneal transplantation specific PROM will be useful in clinical settings to compare the outcomes of different surgical techniques from the patient perspective.

Vision-related quality of life with myopia management: A review

The disease of myopia has come into focus as a worldwide public health concern. Myopia has shown increasing prevalence, incidence at earlier age and progression to a higher degree. Progressive increase in degree of myopia is strongly associated with increase in axial length of the eye. Various interventions have been shown to slow axial elongation in children. These interventions have been studied to assess efficacy in slowing axial elongation and correction of vision. In addition, research into quality of vision, risk of adverse events, overall safety and impact on vision-related quality (VR-QoL) of life has been pursued. In contrast, studies have been published to demonstrate the risks of myopia, high myopia and increased axial length. This review will discuss VR-QoL assessment on the most effective and most commonly prescribed interventions to slow axial elongation and myopia progression. The patient attributes considered are VR-QoL scores from validated instruments. The development and use of validated survey instruments to assess the patient-reported outcomes is discussed. The review demonstrates that there are numerous factors that may impact VR-QoL to evaluate in the decision-making process when eye care providers consider when, how and if to prescribe myopia management (MM) for children with myopia.

Quality of life study in ophthalmic practice

The article discusses various methods for studying the quality of life in all kinds of eye diseases. General and special questionnaires used in modern ophthalmological practice are presented. The presence of a sufficiently large amount of data indicating the relationship between the quality of life and objective indicators of the visual system was established. A fairly good comparability of results obtained in the assessment of various quality of life questionnaires in a patient with ophthalmic condition was revealed.

Quality of Life in Presbyopes with Low and High Myopia Using Single-Vision and Progressive-Lens Correction

This study evaluates the impact of the severity of myopia and the type of visual correction in presbyopia on vision-related quality of life (QOL), using the refractive status and vision profile (RSVP) questionnaire. A total of 149 subjects aged 41-75 years with myopic presbyopia were recruited: 108 had low myopia and 41 had high myopia. The RSVP questionnaire was administered. Rasch analysis was performed on five subscales: perception, expectation, functionality, symptoms, and problems with glasses. Highly myopic subjects had a significantly lower mean QOL score (51.65), compared to low myopes (65.24) (p < 0.001). They also had a significantly lower functionality score with glasses (49.38), compared to low myopes (57.00) (p = 0.018), and they had a worse functionality score without glasses (29.12), compared to low myopes (36.24) (p = 0.045). Those who wore progressive addition lenses (PAL) in the high-myope group (n = 25) scored significantly better, compared to those who wore single-vision distance (SVD) lenses (n = 14), with perception scores of 61.19 and 46.94, respectively (p = 0.029). Highly myopic presbyopes had worse overall QOL and functionality, both with and without glasses, compared to presbyopes with low myopia. High-myopic PAL users had a better perception outcome than SVD lens wearers. Low-myopic PAL wearers had a better QOL than SVD wearers.

Impact of incident age-related macular degeneration and associated vision loss on vision-related quality of life

BACKGROUND

We examined the associations between the 6-year incidence of age-related macular degeneration (AMD) and vision-related quality of life (VRQoL), and the contribution of presenting visual acuity (VA), in an Asian population.

METHODS

Fundus images from the Singapore Chinese Eye Study, a population-based cohort study (baseline: 2009-2011; follow-up: 2015-2017), were graded using a modified Wisconsin age-related maculopathy grading system. Incident AMD was defined as no baseline AMD in both eyes and early/late AMD in the worse eye at follow-up. Presenting VA was assessed using the logarithm of the minimum angle of resolution chart at 4 m under standard lighting conditions with habitual correction. Multiple linear regression models determined the associations between AMD incidence with changes in the Rasch-transformed scores of the Reading, Mobility and Emotional VRQoL domains of the 32-item Impact of Visual Impairment (IVI-32) questionnaire, adjusted for traditional confounders. The contribution of presenting VA to changes in VRQoL was also estimated.

RESULTS

Of the 2251 participants without AMD at baseline (mean age (SD): 57.7 (9) years, 51.4% women), 101 (4.5%) and 11 (0.5%) developed incident early and late AMD at follow-up, respectively. Incident late AMD was associated with significant 30.3%, 32.5% and 30.9% decrements in Reading, Mobility and Emotional IVI scores, respectively. The contribution of presenting VA ranged between 1.62% and 4.35% of the observed decrements. No significant associations were noted with incident early AMD.

CONCLUSION

Incident late AMD had a substantial impact on all aspects of VRQoL, with presenting VA contributing only minimally to this longitudinal relationship.

Validation of a New Diabetic Retinopathy Knowledge and Attitudes Questionnaire in People with Diabetic Retinopathy and Diabetic Macular Edema

Purpose

A validated questionnaire assessing diabetic retinopathy (DR)- and diabetic macular edema (DME)-related knowledge (K) and attitudes (A) is lacking. We developed and validated the Diabetic Retinopathy Knowledge and Attitudes (DRKA) questionnaire and explored the association between K and A and the self-reported difficulty accessing DR-related information (hereafter referred to as Access).

Methods

In this mixed-methods study, eight focus groups with 36 people with DR or DME (mean age, 60.1 ± 8.0 years; 53% male) were conducted to develop content (phase 1). In phase 2, we conducted 10 cognitive interviews to refine item phrasing. In phase 3, we administered 28-item K and nine-item A pilot questionnaires to 200 purposively recruited DR/DME patients (mean age, 59.0 ± 10.6 years; 59% male). The psychometric properties of DRKA were assessed using Rasch and classical methods. The association between K and A and DR-related Access was assessed using univariable linear regression of mean K/A scores against Access.

Results

Following Rasch-guided amendments, the final 22-item K and nine-item A scales demonstrated adequate psychometric properties, although precision remained borderline. The scales displayed excellent discriminant validity, with K/A scores increasing as education level increased. Compared to those with low scores, those with high K/A scores were more likely to report better access to DR-related information, with K scores of 0.99 ± 0.86 for no difficulty; 0.79 ± 1.05 for a little difficulty; and 0.24 ± 0.85 for moderate or worse difficulty (P < 0.001).

Conclusions

The psychometrically robust 31-item DRKA questionnaire can measure DR- and DME-related knowledge and attitudes.

Translational Relevance

The DRKA questionnaire may be useful for interventions to improve DR-related knowledge and attitudes and, in turn, optimize health behaviors and health literacy.

Patient-reported outcome measures in presbyopia: a literature review

Presbyopia is the age-related loss of near-distance focusing ability. The aim of this study was to identify patient-reported outcome measures (PROMs) used in clinical trials and quality-of-life studies conducted in individuals with presbyopia and to assess their suitability for use in individuals with phakic presbyopia. Literature searches were performed in Medline and Embase up until October 2017. Specific search terms were used to identify presbyopia studies that included a PROM. All clinical trials with PROM-supported endpoints in presbyopia were identified on ClinicalTrials.gov. Further searches were conducted to retrieve articles documenting the development and psychometric evaluation of the PROMs identified. A total of 703 records were identified; 120 were selected for full-text review. Twenty-one clinical trials employed PROMs to support a primary or secondary endpoint. In total, 13 PROMs were identified; a further 23 publications pertaining to the development and validation of these measures were retrieved. Most PROMs were developed prior to release of the Food and Drug Administration (FDA) 2009 patient-reported outcome guidance and did not satisfy regulatory standards. The Near Activity Visual Questionnaire (NAVQ) was identified as the most appropriate for assessing near-vision functioning in presbyopia. While the NAVQ was developed in line with the FDA guidance, the items do not reflect changes in technology that have occurred since the questionnaire was developed in 2008 (eg, the increase in smartphone use), and the measure was not validated in a purely phakic presbyopia sample. Further research is ongoing to refine the NAVQ to support trial endpoints related to changes in near-vision functioning associated with phakic presbyopia.

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

SIGNIFICANCE

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The use of WaveLight Contoura to create a uniform cornea: 6-month results with subjective patient surveys

Purpose

The aim of this study was to report on the 6-month visual results of Contoura with Layer Yolked Reduction of Astigmatism (LYRA) protocol, as well as the subjective patient-reported outcomes (PRO) by standardized survey.

Patients and methods

A retrospective analysis was conducted in 50 consecutive eyes with 6-month results that had bilateral Contoura laser-assisted in situ keratomileusis (LASIK) correction of measured astigmatism and axis using the LYRA protocol. PRO were measured via the Refractive Status and Vision Profile (RSVP) standardized survey. Objective visual results, subjective patient results, and rates of regression were reported.

Results

Most (78%) of the eyes achieved an uncorrected visual acuity (UCVA) of 20/15 and 98% of the eyes achieved an UCVA of 20/20 vision after primary correction. After enhancements, the percentage of uncorrected eyes achieving 20/15 vision was 90 and 20/20 vision was 100. RSVP patient-related outcomes showed that all patients (100%) were either satisfied or very satisfied with their vision. Most patients (21/25, 84%) were very satisfied. On a numerical ordinal scale of 1–10 (where 10 is the best vision), as reported by patients post-operative (post-op), 15 (60%) patients reported a vision score of 10, nine (36%) patients reported a score of 9, and one (4%) patient reported a score of 8. Initial correction was accurate on all patients, but nine eyes had refractive error changes due to epithelial masking of higher order aberrations (HOAs) over the follow-up period, a number that was also likely artificially high due to study bias.

Conclusion

Contoura measured axis and astigmatism-eliminated HOA, resulting in a more uniform cornea with an accurate removal of astigmatism, excellent 20/15 and 20/20 visual outcomes, and favorable patient-reported subjective outcomes.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

Impact of Incidence and Progression of Diabetic Retinopathy on Vision-Specific Functioning

PURPOSE

To investigate the independent impact of the incidence and progression of diabetic retinopathy (DR) on visual functioning (VF).

DESIGN

Population-based cohort study.

PARTICIPANTS

A total of 518 participants aged 40 to 80 years (baseline visit 2007-2009 and second visit 6 years later, 2013-2015), with diabetes, clinical data, and VF information at both visits.

MAIN OUTCOME MEASURES

VF-7 scores, converted to interval-level person measures (in logits) using Rasch analysis.

METHODS

Incident DR was defined using the Modified Airlie House classification as "none or minimal" DR at baseline and at least mild nonproliferative DR at follow-up; incident vision-threatening DR (VTDR; severe nonproliferative DR, proliferative DR, and/or clinically significant macular edema) as no VTDR at baseline, and present at follow-up; and DR progression as at least a 1-step worsening in DR at follow-up from mild or worse status at baseline. The longitudinal associations between incident DR, VTDR, and DR progression, as well as change in composite and individual item scores of VF, were assessed using multivariable linear regression models.

RESULTS

Of the 518 participants (mean age ± standard deviation [SD] 59.8±9.0 years; 47.7% female), 42 (9.8%), 14 (2.8%), and 32 (42.7%) had incident DR, incident VTDR, and DR progression, respectively, at follow-up. In models adjusting for traditional confounders, persons with incident DR and VTDR had a 13.7% (β = -0.60; 95% confidence interval [CI], -0.96 to -0.24; P = 0.001) and 23% (β = -1.00; 95% CI, -1.61 to -0.38; P = 0.001) reduction in mean VF scores at follow-up. Furthermore, individuals with incident DR had similar independent reductions in scores for 7 individual items of the VF-7, whereas those with incident VTDR had the largest reductions for activities like cooking (31%; P = 0.003), reading the newspaper (29.6%; P < 0.001), and seeing street signs (28%, P = 0.001) at follow-up. Progression of DR was not independently associated with change in overall VF (β = -0.18; 95% CI, -1.00, 0.64; P = 0.660).

CONCLUSIONS

Incident DR, particularly vision-threatening stages, has a substantial negative impact on people's overall vision-dependent functioning and specific activities such as cooking, seeing street signs, and reading the newspaper. Our findings reinforce the need for strategies to prevent or delay the development of DR.

Rasch Analysis of the Standard Patient Evaluation of Eye Dryness Questionnaire

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Patient-reported Outcomes for Assessment of Quality of Life in Refractive Error: A Systematic Review

SIGNIFICANCE

This review has identified the best existing patient-reported outcome (PRO) instruments in refractive error. The article highlights the limitations of the existing instruments and discusses the way forward.

PURPOSE

A systematic review was conducted to identify the types of PROs used in refractive error, to determine the quality of the existing PRO instruments in terms of their psychometric properties, and to determine the limitations in the content of the existing PRO instruments.

METHODS

Articles describing a PRO instrument measuring 1 or more domains of quality of life in people with refractive error were identified by electronic searches on the MEDLINE, PubMed, Scopus, Web of Science, and Cochrane databases. The information on content development, psychometric properties, validity, reliability, and responsiveness of those PRO instruments was extracted from the selected articles. The analysis was done based on a comprehensive set of assessment criteria.

RESULTS

One hundred forty-eight articles describing 47 PRO instruments in refractive error were included in the review. Most of the articles (99 [66.9%]) used refractive error-specific PRO instruments. The PRO instruments comprised 19 refractive, 12 vision but nonrefractive, and 16 generic PRO instruments. Only 17 PRO instruments were validated in refractive error populations; six of them were developed using Rasch analysis. None of the PRO instruments has items across all domains of quality of life. The Quality of Life Impact of Refractive Correction, the Quality of Vision, and the Contact Lens Impact on Quality of Life have comparatively better quality with some limitations, compared with the other PRO instruments.

CONCLUSIONS

This review describes the PRO instruments and informs the choice of an appropriate measure in refractive error. We identified need of a comprehensive and scientifically robust refractive error-specific PRO instrument. Item banking and computer-adaptive testing system can be the way to provide such an instrument.

Impact of type I Boston keratoprosthesis implantation on vision-related quality of life

Aim

To determine the impact of type I Boston keratoprosthesis (KPro) implantation on vision-related quality of life (VRQoL).

Methods

Prospective study in 33 patients (mean age 56±12 years, 67% male) with bilateral corneal blindness, who underwent a KPro implantation at a single tertiary eye hospital (June 2011–July 2015). VRQoL was evaluated using the Impact of Vision Impairment Questionnaire (IVI) at baseline and at 3–6 months postsurgery, after stabilisation of best-corrected visual acuity (BCVA). Rasch analysis was used to transform the IVI responses into interval-level measures comprising the ‘reading’, ‘mobility’ and ‘emotional’ subscales with effect sizes calculated for pre-post VRQoL scores.

Results

Mean preoperative BCVA was counting-fingers at 2 feet in the operated eye (20/240 fellow eye). Preoperative VRQoL scores: −2.27, –2.91 and −3.06 logits for the reading, mobility and emotional subscales, respectively. Device retention rate was 90% over the follow-up period (mean 26±12 months). We observed large gains for reading and mobility of 1.92 logits (effect size 0.88), and 2.64 logits (effect size 0.89) respectively, with a moderate gain in the emotional subscale of 2.11 logits (effect size 0.59). These improvements did not vary significantly with BCVA on multivariate analysis (all p>0.05).

Conclusion

We observed a differential short-term improvement to VRQoL after KPro implantation with a significant impact on emotional well-being, which may not be fully explained by visual improvement alone. Further studies are required to confirm if these improvements in VRQoL are sustained in the long-term and are generalisable to other populations.

Prevalence, Correlates, and Impact of Uncorrected Presbyopia in a Multiethnic Asian Population

PURPOSE

To examine the prevalence, correlates, and impact of uncorrected presbyopia on vision-specific functioning (VF) in a multiethnic Asian population.

DESIGN

Population-based cross-sectional study.

METHODS

We included 7890 presbyopic subjects (3909 female; age range, 40-86 years) of Malay, Indian, and Chinese ethnicities from the Singapore Epidemiology of Eye Disease study. Presbyopia was classified as corrected and uncorrected based on self-reported near correction use. VF was assessed with the VF-11 questionnaire validated using Rasch analysis. Multivariable logistic and linear regression models were used to investigate the associations of sociodemographic and clinical parameters with uncorrected presbyopia, and its impact on VF, respectively. As myopia may mitigate the impact of noncorrection, we performed a subgroup analysis on myopic subjects only (n = 2742).

RESULTS

In total, 2678 of 7890 subjects (33.9%) had uncorrected presbyopia. In multivariable models, younger age, male sex, Malay and Indian ethnicities, presenting distance visual impairment (any eye), and lower education and income levels were associated with higher odds of uncorrected presbyopia (all P < .05). Compared with corrected presbyopia, noncorrection was associated with worse overall VF and reduced ability to perform individual near and distance vision-specific tasks even after adjusting for distance VA and other confounders (all P < .05). Results were very similar for myopic individuals.

CONCLUSION

One-third of presbyopic Singaporean adults did not have near correction. Given its detrimental impact on both near and distance VF, public health strategies to increase uptake of presbyopic correction in younger individuals, male individuals, and those of Malay and Indian ethnicities are needed.

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

Background

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

Methods

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

Results

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

Conclusions

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

The patient health questionnaire-9: validation among patients with glaucoma

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.

Quality assessment of ophthalmic questionnaires: review and recommendations

PURPOSE

The aim of this article was to systematically review all the available ophthalmic patient-reported outcome (PRO) instruments (questionnaires) that demonstrated interval measurement properties to identify the instruments with the highest psychometric quality for use in different eye diseases and conditions.

METHODS

An extensive literature review was carried out to identify all existing ophthalmic PRO instruments. Instruments were then excluded if they did not have demonstrable interval measurement properties; the remaining instruments were reviewed. The quality of the following psychometric properties was assessed: content development (initial item development process), performance of the response scale, dimensionality (whether the instrument measures a single construct), measurement precision, validity (convergent, concurrent, discriminant, and known groups), reliability (test-retest), targeting (whether the items are appropriate [e.g., difficulty level] for the population), differential item functioning (whether subgroups of people respond differently to an item), and responsiveness.

RESULTS

The search identified 48 PRO instruments that demonstrated interval measurement properties, and these were relevant to nine applications: glaucoma, dry eye, refractive errors, cataract, amblyopia and strabismus, macular diseases, adult low vision, children low vision, and others. These instruments were evaluated against the psychometric property quality criteria and were rated for quality based on the number of criteria met.

CONCLUSIONS

This review provides a descriptive catalog of ophthalmic PRO instruments to inform researchers and clinicians on the choice of the highest-quality PRO instrument suitable for their purpose.

An enhanced functional ability questionnaire (faVIQ) to measure the impact of rehabilitation services on the visually impaired

AIM

To develop a short, enhanced functional ability Quality of Vision (faVIQ) instrument based on previous questionnaires employing comprehensive modern statistical techniques to ensure the use of an appropriate response scale, items and scoring of the visual related difficulties experienced by patients with visual impairment.

METHODS

Items in current quality-of-life questionnaires for the visually impaired were refined by a multi-professional group and visually impaired focus groups. The resulting 76 items were completed by 293 visually impaired patients with stable vision on two occasions separated by a month. The faVIQ scores of 75 patients with no ocular pathology were compared to 75 age and gender matched patients with visual impairment.

RESULTS

Rasch analysis reduced the faVIQ items to 27. Correlation to standard visual metrics was moderate (r=0.32-0.46) and to the NEI-VFQ was 0.48. The faVIQ was able to clearly discriminate between age and gender matched populations with no ocular pathology and visual impairment with an index of 0.983 and 95% sensitivity and 95% specificity using a cut off of 29.

CONCLUSION

The faVIQ allows sensitive assessment of quality-of-life in the visually impaired and should support studies which evaluate the effectiveness of low vision rehabilitation services.

The impact of anti-vascular endothelial growth factor treatment on quality of life in neovascular age-related macular degeneration

PURPOSE

To assess the impact of anti-vascular endothelial growth factor (VEGF) treatment in routine medical practice on vision-related quality of life (VRQoL) in neovascular age-related macular degeneration (AMD).

DESIGN

Prospective case series.

PARTICIPANTS

A total of 169 patients with neovascular AMD undergoing anti-VEGF treatment.

METHODS

The VRQoL interviews at baseline (n = 169), 6 months (n = 138), and 12 months (n = 120), routine anti-VEGF treatment with up to monthly follow-ups, and re-treatment as indicated. The Impact of Vision Impairment (IVI) questionnaire was subjected to Rasch analysis to assess its measurement performance and generate interval-level estimates of VRQoL at all time points, anchoring the instrument to its baseline measurement characteristics. Factors associated with a change in reported VRQoL were assessed using generalized linear regression models.

MAIN OUTCOME MEASURES

The VRQoL as measured by the IVI using its 3 subscales: Accessing Information, Mobility, and Emotional Well-being.

FINDINGS

The mean age was 70 years (±6 years standard deviation [SD]); 56% were female. Visual acuity (VA) improved by a mean of 8 letters (±17 SD), and mean retinal thickness decreased by 87 (±89.7) μm with an average of 6.5 (±2.6) injections over 12 months. Those who lost >2 lines (n = 13, 11%) reported worse VRQoL at 12 months on the Accessing Information and Mobility subscales (P = 0.007 and P = 0.050, respectively). Conversely, those who gained >2 lines (n = 29, 24%) reported better VRQoL on the Accessing Information and Emotional Well-being subscales (P = 0.009 and P = 0.008, respectively). Patients who did not experience a change in VA reported no change in their VRQoL. In multivariate analyses, only a change in VA but not whether the better or worse eye was treated predicted a change in VRQoL on the Accessing Information (P = 0.004) and the Emotional Well-being (P = 0.008) subscales.

CONCLUSIONS

We confirmed that anti-VEGF treatment for neovascular AMD improves patients' VRQoL in those who gain vision and maintains VRQoL in those who maintain VA in their treated eye, irrespective of whether the worse or better eye is treated. Against this background, the best possible outcomes should be aimed for even if the worse eye is treated because a loss of VA in the worse eye will adversely affect patients' VRQoL.

A randomized, single-center study of equivalence of 2 intraocular lenses used in cataract surgery

PURPOSE

To compare the outcomes of 2 intraocular lenses (IOLs) for the treatment of age-related cataracts.

DESIGN

Prospective, randomized trial.

PARTICIPANTS

Patients with age-related cataracts were recruited and randomized to receive phacoemulsification and implantation of either the AcrySof SA60AT lens (Alcon, Inc, Fort Worth, TX) or the low-cost Tecsoft Flex lens (Fred Hollows Foundation, Tilganga, Nepal). A total of 300 patients were available for description and analysis (148 in the AcrySof group and 152 in the Tecsoft group).

METHODS

Patients underwent phacoemulsification and implantation of the AcrySof SA60AT lens or the Tecsoft Flex lens. They were followed up and examined at baseline, 1 week, 1 month, 6 months, and 12 months after cataract surgery.

MAIN OUTCOME MEASURES

Uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BDVA), incidence of posterior capsule opacification (PCO), Visual Function Index questionnaire results, and safety of the implanted IOLs.

RESULTS

No significant difference (P>0.05) was found in UDVA and BDVA after surgery between the 2 groups. The equivalence test of the 95% confidence intervals showed that both lenses had an equal improvement of UDVA and BDVA as well as similar rates of PCO after cataract surgery. There was no significant difference between the 2 groups with regard to visual functioning or the incidence of adverse surgical events during (P>0.05) or after (P>0.05) the surgery.

CONCLUSIONS

The Tecsoft Flex IOL is a low-cost suitable alternative that is similar to the AcrySof IOL in terms of safety and visual outcomes.

Visual function after correction of distance refractive error with ready-made and custom spectacles: a randomized clinical trial

PURPOSE

To evaluate patient-reported outcome measures with the use of ready-made spectacles (RMS) and custom spectacles (CS) in an adult population in India with uncorrected refractive error (URE).

DESIGN

Prospective, double-masked, randomized trial with 1-month follow-up.

PARTICIPANTS

A total of 363 adults aged 18 to 45 years with ≥1 diopter (D) of URE (RMS, n = 183; CS, n = 180).

INTERVENTION

All participants received complete refraction and were randomized to receive CS (full sphero-cylindrical correction) or RMS based on the spherical equivalent for the eye with lower refractive error but limited to the powers in the RMS inventory.

MAIN OUTCOME MEASURES

Visual function and quality of life (VFQoL) instrument and participant satisfaction.

RESULTS

Rasch scores for VFQoL increased from 1.14 to 4.37 logits in the RMS group and from 1.11 to 4.72 logits in the CS group: respective mean changes of 3.23 (95% confidence interval [CI], 2.90-3.56) vs. 3.61 (95% CI, 3.34-3.88), respectively. Mean patient satisfaction also increased by 1.83 points (95% CI, 1.60-2.06) on a 5-point Likert scale in the RMS group and by 2.04 points (95% CI, 1.83-2.24) in the CS group. In bivariate analyses, CS was not associated with increased VFQoL or patient satisfaction compared with the RMS group. In the full multivariable linear regression, the CS group had greater improvement when compared with those receiving RMS (+0.45 logits; 95% CI, 0.02-0.88), and subjects with astigmatism >2.00 D had significantly less improvement (-0.99 logits; 95% CI, -1.68 to -0.30) after controlling for demographic and vision-related characteristics. In multivariable analysis, increased change in patient satisfaction was related to demographic and optical characteristics, but not spectacle group.

CONCLUSIONS

Ready-made spectacles produce large but slightly smaller improvements in VFQoL and similar satisfaction with vision at 1-month follow-up when compared with CS. Ready-made spectacles are suitable for the majority of individuals with URE in our study population, although those with high degrees of astigmatism may benefit from a trial of CS. This study provides further evidence for the use of RMS in settings where CS are unavailable or unaffordable, or refractive services are inaccessible to those in need.

Impact of bilateral open and closed-angle glaucoma on glaucoma-specific functioning in Asians

PURPOSE

To evaluate the impact of bilateral primary glaucoma on glaucoma-specific functioning in Asians.

METHODS

Patients with bilateral primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) aged 40 years or above of Chinese ethnicity in Singapore were recruited. All underwent a comprehensive clinical assessment of glaucoma. Glaucoma was diagnosed with a standard criteria including optic disc abnormality and visual field defect. The Glaucoma Quality of Life-15, a glaucoma-specific questionnaire, was used to evaluate the impact of glaucoma, and Rasch analysis was used to validate the Glaucoma Quality of Life-15.

RESULTS

A total of 192 patients (mean±SD age, 65.73±17.6 y and 65.1% male) were recruited, of which 56.2% (n=108) and 43.8% (n=84) had POAG and PACG, respectively. Fifty-four (28.1%), 85 (44.3%), and 53 (27.6%) had bilateral mild glaucoma, mild glaucoma in 1 eye and moderate/severe glaucoma in the other, and bilateral moderate/severe glaucoma, respectively. In multivariate analyses, compared with patients with mild glaucoma in both eyes, those with (a) mild glaucoma in 1 eye and moderate/severe in other; and (b) moderate/severe glaucoma in both eyes, reported significantly poorer functioning (β-coefficient=-8.20; confidence interval, -14.36 to -2.04; P<0.05) and (β=-21.05; confidence interval, -28.06 to -14.04; P<0.05), respectively. A similar independent association was found for POAG and PACG. These associations were also considered to be clinically significant while comparing bilateral mild glaucoma with bilateral moderate/severe glaucoma. We however, found no significant difference for functioning and severity of glaucoma between PACG and POAG patients (P<0.05).

CONCLUSIONS

Bilateral glaucoma is worse than the mild form in any eye and is significantly associated with poor glaucoma-specific functioning in this Singaporean Chinese sample. These data emphasize the need for strategies to identify patients early and prevent deterioration beyond the mild form of the condition.

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.

Rasch analysis of the Ocular Surface Disease Index (OSDI)

PURPOSE

The Ocular Surface Disease Index (OSDI) is a 12-item scale for the assessment of symptoms related to dry eye disease and their effect on vision. Its reliability and validity have been investigated within the classical test theory framework and, more recently, using Rasch analysis. The purpose of the present analysis was to more completely investigate the functioning of its response category structure, the validity of its three subscales, and the unidimensionality of the latent construct it is intended to assess.

METHODS

Responses to the OSDI from 172 females participating in the Dry Eye in Postmenopause (DEiM) study who had previously been diagnosed with dry eye or reported significant ocular irritation and dryness were analyzed. Response category structure and item fit statistics were evaluated for assessment of model fit. Person separation statistics were used to examine the validity of the subscales. Unidimensionality was assessed by principal component analysis (PCA) of model residuals.

RESULTS

The recommended five-category response structure resulted in disordered response thresholds. A four-category structure resulted in ordered thresholds. Item infit statistics were acceptable for all 12 items. Person separation with this category structure was adequate, with a person separation index of 2.16. None of the three subscales demonstrated adequate person separation. PCA showed one other significant factor onto which the three environmental items loaded significantly.

CONCLUSIONS

All items demonstrated acceptable fit to the model after collapsing categories to order the response thresholds. The original subscales did not prove valid, and there is some evidence of multidimensionality and poor targeting.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Comparison of scoring approaches for the NEI VFQ-25 in low vision

PURPOSE

The aim of this study was to evaluate different approaches to scoring the National Eye Institute Visual Functioning Questionnaire-25 (NEI VFQ-25) in patients with low vision including scoring by the standard method, by Rasch analysis, and by use of an algorithm created by Massof to approximate Rasch person measure. Subscale validity and use of a 7-item short form instrument proposed by Ryan et al. were also investigated.

METHODS

NEI VFQ-25 data from 50 patients with low vision were analyzed using the standard method of summing Likert-type scores and calculating an overall average, Rasch analysis using Winsteps software, and the Massof algorithm in Excel. Correlations between scores were calculated. Rasch person separation reliability and other indicators were calculated to determine the validity of the subscales and of the 7-item instrument.

RESULTS

Scores calculated using all three methods were highly correlated, but evidence of floor and ceiling effects was found with the standard scoring method. None of the subscales investigated proved valid. The 7-item instrument showed acceptable person separation reliability and good targeting and item performance.

CONCLUSIONS

Although standard scores and Rasch scores are highly correlated, Rasch analysis has the advantages of eliminating floor and ceiling effects and producing interval-scaled data. The Massof algorithm for approximation of the Rasch person measure performed well in this group of low-vision patients. The validity of the subscales VFQ-25 should be reconsidered.

Psychometric properties of visual functioning index using Rasch analysis

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.

Remediating serious flaws in the National Eye Institute Visual Function Questionnaire

PURPOSE

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

SETTING

Flinders Medical Centre, Adelaide, Australia.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Impact of diabetic retinopathy on vision-specific function

OBJECTIVE

To assess the influence of the spectrum of diabetic retinopathy (DR) on vision-specific function in an Asian population.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Persons aged 40 to 80 years of Malay ethnicity in Singapore.

METHODS

The Singapore Malay Eye Study was a population-based, cross-sectional study of 3280 Asian Malays (78.7% response rate). Five end points were considered: (1) any DR, (2) macular edema (ME), (3) clinically significant macular edema (CSME), (4) vision-threatening DR (VTDR), and (5) DR severity levels ranging from none to proliferative diabetic retinopathy (PDR). Vision function was assessed using the Vision-Specific Functioning Scale validated using Rasch analysis.

MAIN OUTCOME MEASURES

Vision-specific functioning score.

RESULTS

Of 357 diabetic participants in the study, 23.2% had any DR, 5.6% had ME, 5.0% had CSME, 10.6% had VTDR, and 6.2% had PDR. In linear regression models adjusting for age, gender, stroke, diabetic risk factors, and socioeconomic factors, poorer vision-specific function was associated independently with any DR (beta, -0.21; P<0.05), ME (beta, -0.48; P<0.05), CSME (beta, -0.42; P<0.05), VTDR (beta, -0.64; P<0.05), and PDR (beta, -0.92; P<0.001). When controlling further for presenting visual acuity, VTDR (beta, -0.37; P = 0.01) and PDR (beta, -0.61; P = 0.002) were the only 2 DR categories independently associated with poorer vision-specific function and PDR. Persons with VTDR and PDR were 6 to 12 times more likely to report lower participation in daily living activities than those without these DR levels.

CONCLUSIONS

People with VTDR and PDR have substantial difficulty undertaking vision-specific daily activities. These findings reinforce the importance of preventative efforts targeted at the earliest DR stages to prevent progression to later stages of DR.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.