Development and validation of the 21-item children's vision for living scale (CVLS) by Rasch analysis

Amblyopia and the whole child

Amblyopia is a disorder of neurodevelopment that occurs when there is discordant binocular visual experience during the first years of life. While treatments are effective in improving visual acuity, there are significant individual differences in response to treatment that cannot be attributed solely to difference in adherence. In this considerable variability in response to treatment, we argue that treatment outcomes might be optimized by utilizing deep phenotyping of amblyopic deficits to guide alternative treatment choices. In addition, an understanding of the broader knock-on effects of amblyopia on developing visually-guided skills, self-perception, and quality of life will facilitate a whole person healthcare approach to amblyopia.

Engaging the Voices of Children: A Scoping Review of How Children and Adolescents Are Involved in the Development of Quality-of-Life-Related Measures

OBJECTIVES

Patient-reported outcomes are increasingly recommended to guide patient care, develop and evaluate interventions, and modify health systems. However, not enough is known about whether and how children and adolescents, as "experts" in their own health and quality of life (QoL), are being engaged in the development of instruments. Our goals in this review were (1) to identify all QoL-related instruments that have included children and/or adolescents in the development of questionnaire content, including identification of themes and items; and (2) to report how this was done; and (3) to highlight those that used qualitative methods.

METHODS

MEDLINE and Embase were searched for child- or adolescent-completed QoL-related instruments, supplemented by hand-searching of relevant reviews until 2020. Original development papers were identified and retrieved when possible, from which instrument characteristics and details of qualitative development methods were extracted.

RESULTS

We identified 445 instruments, of which 88 used qualitative methods for content development. Interviews and focus groups were the most common methods. A variety of play techniques were used to engage the child and adolescent participants. The specific criteria for the inclusion of children and adolescents (age, developmental stage, duration, and nonclinical location) varied considerably.

CONCLUSIONS

Researchers frequently involve children and adolescents in qualitative methods when developing QoL-related measures; however, there is little information about the methods used. Better reporting of methodology, improved dissemination of methods guidelines, and research into optimal ways of including children and adolescents in the process of instrument development would be useful.

A Patient-reported Outcome Measure of Functional Vision for Children and Young People Aged 8 to 18 Years With Visual Impairment

PURPOSE

To develop age-appropriate extensions of a patient-reported outcome measure for capturing the functional impact of visual impairment on daily activities of children and young people aged 8 up to 18 years.

DESIGN

Questionnaire development and validation study.

METHODS

Pediatric Ophthalmology departments at Great Ormond Street Hospital and Moorfields Eye Hospital, and, in the final study phase, 20 further UK hospitals. Children and young people (aged 6-19 years) with visual impairment (acuity of the logarithm of the minimum angle of resolution (LogMAR) worse than 0.50 in the better eye) due to any cause but without significant non-ophthalmic impairments. We used our prototype FVQ_CYP for 10-15 year olds as the foundation. Twenty-nine semi-structured interviews confirmed relevance of existing, and identified new, age-specific items. Twenty-eight cognitive interviews captured information regarding comprehensibility and format. The FVQ_Child (8-12 years) and FVQ_Young Person (13-18 years) were evaluated with a national sample of 113 children and 96 young people using Rasch analysis.

RESULTS

Issues emerging from interviews with children and young people were largely congruent with those elicited originally with 10-15 year olds. The 28-item FVQ_Child and 38-item FVQ_Young Person versions have goodness-of-fit statistics within the interval 0.5, 1.5 and person separation values of 5.87 and 6.09 respectively. Twenty-four overlapping "core" items enabled their calibration on the same measurement scale. Correlations with acuity (r = 0.47) demonstrated construct validity.

CONCLUSIONS

The FVQ_C and FVQ_Young Person are robust age-appropriate versions of the FVQ_CYP which can be used cross-sectionally or sequentially/longitudinally across the age range of 8 up to 18 years in clinical practice and research.

Development of Pediatric Eye Questionnaires for Children With Eye Conditions

PURPOSE

To develop patient-derived Pediatric Eye Questionnaires (PedEyeQ) to separately assess eye-related quality of life (ER-QOL) and functional vision in children with eye conditions.

DESIGN

Questionnaire development study.

METHODS

A total of 444 children (0 to <18 years old), across 10 diagnostic categories, were enrolled at 2 sites. All parents (n = 444) and 277 children (5 to <18 years old) completed master questionnaires, developed from patient-derived concerns. Factor analysis was performed to identify unidimensional domains (eigenvalue >1.0) and Rasch analyses (differential item functioning, targeting, fit) to reduce items (separate analyses for subjects aged 0-4, 5-11, and 12-17 years and for each factor).

RESULTS

The Child 5- to 11-year-old PedEyeQ consisted of 4 unidimensional domains/questionnaires: functional vision, bothered by eyes/vision, social, frustration/worry (10 items each). The Child 12- to 17-year-old PedEyeQ consisted of the same 4 domains (total 39 items). The Proxy 0- to 4-year-old PedEyeQ consisted of 3 questionnaires/domains: functional vision, bothered by eyes/vision, social (total 29 items). The Proxy 5- to 11-year-old PedEyeQ consisted of 5 questionnaires/domains: functional vision, bothered by eyes/vision, social, frustration/worry, eye care (total 39 items), as did the Proxy 12- to 17-year-old PedEyeQ (total 42 items). The Parent PedEyeQ consisted of 4 questionnaires/domains: impact on parent/family, worry regarding child's eye condition, worry regarding child's self-perception and interactions, worry regarding child's visual function (total 35 items). Rasch look-up tables were created for scoring.

CONCLUSIONS

By following a rigorous approach, we have developed Pediatric Eye Questionnaires for separately assessing functional vision and ER-QOL domains in children of any age and with any eye condition.

Patient-derived questionnaire items for patient-reported outcome measures in pediatric eye conditions

PURPOSE

To identify specific health-related quality of life (HRQOL) and functional vision concerns of children with eye conditions, and create comprehensive lists of potential questionnaire items as a first step in developing patient-reported outcome measures.

METHODS

Children experiencing a range of pediatric eye conditions, along with one of their parents, were interviewed to identify specific concerns. Transcribed interviews were reviewed, and specific HRQOL and functional vision concerns were coded independently by two reviewers. Coded concerns were reviewed to formulate questions to address specific child concerns (derived from child and parent interviews) and specific parent concerns. Questions were grouped into bins of like questions. Two comprehensive lists of questions were formulated, one addressing child-related concerns and one addressing parent-related concerns.

RESULTS

This study included 180 children and 328 parents. A total of 614 individual child questions were grouped into 36 bins (eg, appearance, coordination, glasses, learning), and 589 parent questions were formulated and grouped into 61 bins (eg, having to assist the child, worry about deterioration, time off work, safety).

CONCLUSIONS

Using rigorous methods based on individual interviews, we identified a comprehensive list of patient- and parent-derived questionnaire items that address functional vision and HRQOL concerns of children with eye conditions and of their parents. We plan to use this large pool of potential questionnaire items to develop a formal set of pediatric outcome measures, and this pool of questions may also be a resource for future research.

Order-Constrained Estimation of Nominal Response Model Parameters to Assess the Empirical Order of Categories

Bock's nominal response model (NRM) is sometimes used to identify the empirical order of response categories in polytomous items but its application tags many items as having disordered categories. Disorderly estimated categories may not reflect a true characteristic of the items but, rather, a numerically best-fitting solution possibly equivalent to other solutions with orderly estimated categories. To investigate this possibility, an order-constrained variant of the NRM was developed that enforces the preassumed order of categories on parameter estimates, for a comparison of its outcomes with those of the original unconstrained NRM. For items with ordered categories, order-constrained and unconstrained solutions should account for the data equally well even if the latter solution estimated disordered categories for some items; for items with truly disordered categories, the unconstrained solution should outperform the order-constrained solution. Criteria for this comparative analysis are defined and their utility is tested in several simulation studies with items of diverse characteristics, including ordered and disordered categories. The results demonstrate that a comparison of order-constrained and unconstrained calibrations on such criteria provides the evidence needed to determine whether category disorder estimated on some items by the original unconstrained form of the NRM is authentic or spurious. Applications of this method to assess category order in existing data sets are presented and practical implications are discussed.

The functional impact of amblyopia

Amblyopia is the most common disorder managed in paediatric ophthalmic practice in industrialised countries. Reports on the impact of amblyopia on tasks relevant to the activities of children, or on skills pertinent to their education and quality of life, is leading to greater understanding of the functional disabilities associated with the condition. This review considers the extent to which amblyopia affects the ability to carry out everyday tasks, with particular attention to studies of motor skills and reading proficiency in children. Collectively, these studies show that amblyopia results in poorer outcomes on tests of skills required for proficiency in everyday tasks and which relate to childhood academic performance. However, the relative contributions that the documented vision anomalies inherent in amblyopia contribute to various functional disabilities is not fully determined. Recent reports have demonstrated improvement following treatment in standardised measures of fine motor skills involved in practical, everyday tasks. Including measurement of functional performance skills in amblyopia treatment trials is desirable to show treatment effect on crucial, real-world activities.

An Analysis of (Dis)Ordered Categories, Thresholds, and Crossings in Difference and Divide-by-Total IRT Models for Ordered Responses

Threshold parameters have distinct referents across models for ordered responses. In difference models, thresholds are trait levels at which responding beyond category k is as likely as responding at or below it; in divide-by-total models, thresholds are trait levels at which responding in category k is as likely as responding in category k - 1. Thus, thresholds in divide-by-total models (but not in difference models) are the crossings of the option response functions for consecutive categories. Thresholds in difference models are always ordered but they may inconsequentially yield ordered or disordered crossings. In contrast, assimilation of thresholds and crossings in divide-by-total models questions category order when crossings are disordered. We analyze these aspects of difference and divide-by-total models, their relation to the order of response categories, and the consequences of collapsing categories to instate ordered crossings under divide-by-total models. We also show that item parameters in models for ordered responses can never contradict the pre-assumed order of categories and that the empirical order can only be established using a polytomous model that does not assume ordered categories, although this often gives rise to spurious outcomes. Practical implications for scale development are discussed.

Comparison of Rating Scales in the Development of Patient-Reported Outcome Measures for Children with Eye Disorders

BACKGROUND

A rating scale is a critical component of patient-reported outcome instrument design, but the optimal rating scale format for pediatric use has not been investigated. We compared rating scale performance when administering potential questionnaire items to children with eye disorders and their parents.

METHODS

Three commonly used rating scales were evaluated: frequency (never, sometimes, often, always), severity (not at all, a little, some, a lot), and difficulty (not difficult, a little difficult, difficult, very difficult). Ten patient-derived items were formatted for each rating scale, and rating scale testing order was randomized. Both child and parent were asked to comment on any problems with, or a preference for, a particular scale. Any confusion about options or inability to answer was recorded.

RESULTS

Twenty-one children, aged 5-17 years, with strabismus, amblyopia, or refractive error were recruited, each with one of their parents. Of the first 10 children, 4 (40%) had problems using the difficulty scale, compared with 1 (10%) using frequency, and none using severity. The difficulty scale was modified, replacing the word "difficult" with "hard." Eleven additional children (plus parents) then completed all 3 questionnaires. No children had problems using any scale. Four (36%) parents had problems using the difficulty ("hard") scale and 1 (9%) with frequency. Regarding preference, 6 (55%) of 11 children and 5 (50%) of 10 parents preferred using the frequency scale.

CONCLUSIONS

Children and parents found the frequency scale and question format to be the most easily understood. Children and parents also expressed preference for the frequency scale, compared with the difficulty and severity scales. We recommend frequency rating scales for patient-reported outcome measures in pediatric populations.