Methods for conceptualising ‘visual ability’ as a measurable construct in children with cerebral palsy

Abstract

BackgroundVision influences functioning and disability of children with cerebral palsy, so there is a growing need for psychometrically robust tools to advance assessment of children’s vision abilities in clinical practice and research. Vision is a complex construct, and in the absence of clarity about this construct it is challenging to know whether valid, reliable measures exist. This study reports a method for conceptualising ‘visual ability’ as a measurable construct.MethodsUsing the items from 19 assessment tools previously identified in a systematic review, this study used a two-phase process: first, deductive content analysis linked items to the International Classification of Functioning, Disability and Health - Child and Youth version (ICF-CY), and second, vision-specific ‘Activity’-level items were explored using inductive thematic analysis.ResultsThe linking and content analysis identified that existing assessment tools are measuring vision across the ICF-CY domains of Body Functions, Activities and Participation, and Environmental and Personal Factors. Items specifically coded to vision at the Activity level were defined as measuring ‘how vision is used’, and these items form the basis of the conceptualisation that ‘visual ability’ is measurable as a single construct.The thematic analysis led to the identification of 3 categories containing 13 themes that reflect a child’s observable visual behaviours. Seven abilities reflect how a child uses vision: responds or reacts, initiates, maintains or sustains looking, changes or shifts looking, searches, locates or finds, and follows. Four interactions reflect the contexts in which a child uses their vision to purposefully interact: watches and visually interacts with people and faces, objects, over distance, and with hands. Finally, two themes reflect a child’s overall use of vision in daily activities: frequency of use, and efficiency of use.ConclusionsThis study demonstrates an approach to exploring and explaining a complex topic utilising World Health Organization language and building on existing research. Despite the complexity of vision, the concept of ‘how vision is used’ can be clearly defined as a measurable construct at the Activity level of the ICF-CY. This study has identified observable visual behaviours that may be developed into items assessing how vision is used in daily activities.Electronic supplementary materialThe online version of this article (doi:10.1186/s12874-017-0316-6) contains supplementary material, which is available to authorized users.

Visual Function Classification System for children with cerebral palsy: development and validation

“…The VFCS was developed empirically following a step‐by‐step process to classify visual abilities of children with CP in everyday life. Visual abilities refer to how the child uses vision purposefully to see, direct gaze, recognize, interact with the environment, and explore it . In fact, while measures of visual impairment, at the level of the eye or brain, are valuable and necessary in the diagnosis and management of children with CP, they do not provide information on how visual dysfunction affects daily life, and do not take into account children's abilities.…”

“…In fact, while measures of visual impairment, at the level of the eye or brain, are valuable and necessary in the diagnosis and management of children with CP, they do not provide information on how visual dysfunction affects daily life, and do not take into account children's abilities. Although some children with CP may show limited levels of functioning and restricted participation due to their visual impairment, others can rely on their visual abilities to overcome their limitations due to motor impairment …”

“…Although vision impairment may markedly affect the quality of life of a child with a developmental disorder, no system is currently available to classify levels of visual functioning analogous to the existing functional classification systems for children with CP . For this reason, a group of experts in the field of CP and visual disorders, with the contribution of parents and patients, set out to develop a new classification system for visual function in children with CP.…”

Cerebral visual impairment and effect of phase-wise stimulation strategies—An interim analysis

“…The plasticity of the visual system and results of previous studies showed that training can enhance visual function which led to the concept of developing training programs matching the nature and degree of visual dysfunction. [ 13 ]…”

Visual Function Classification System for children with cerebral palsy: development of a new tool

“…The work by Baranello et al . to create the VFCS, and the emerging studies of Deramore Denver and her group in Australia to create tools to assess children's visual functioning, complement the few research teams exploring a clinical understanding of the assessment and management of children who grow up with significant challenges in visual functioning …”