Core Outcome Measures in Effectiveness Trials

A Core Outcome Set for children with Cerebral Visual Impairments (COS-CVI)

General Information

In the current climate of financial challenges and limited resources, the importance of best use of available funds is paramount. Core outcome sets are condition-specific sets of outcomes that are developed by and represent the concerns of a range of stakeholders including patients, carers, professionals and policy makers. The aim of this project is to develop a COS for use in evaluative research on interventions that aim to improve outcomes for children with brain-related vision impairments, commonly known as cerebral visual impairments or CVI.

This project is nested within a 5-year programme of work investigating the prevalence, impact and effectiveness of support for primary school age children with CVI. We will use methods recommended by the COMET Initiative (Core Outcome Measures in Effectiveness Trials) including a proportionate review of what’s been measured before; qualitative work to bring in the voices of children and families; a Delphi survey involving parents, children, professionals in medicine and teaching and therapists and a consensus meeting to determine the most important outcomes. We will then review the available tools and decide how best to measure the selected outcomes.

Discussion and Implementation
Our methods are proportionate to the resources available in the 5-year programme and we will reflect and discuss any consequent limitations of this on our findings. We will then use the COS and the tools that best measure the selected outcomes in a feasibility cluster-randomised controlled trial (fcRCT). Outcomes from the fcRCT will include the acceptability and practicality of the COS and these may be useful for further development of the COS.

Ms Cathy Williams
Post: Reader in Paediatric Ophthalmology
Dept: Centre for Child and Adolescent Health, School of Social and Community Medicine
Address: University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN
Tel: 0117 3313388

Dr Anna Pease
Post: Senior Research Associate
Dept: Centre for Child and Adolescent Health, School of Social and Community Medicine
Official Address: University of Bristol, Oakfield House, Oakfield Grove, Bristol, BS8 2BN
Tel: 0117 331 3310

Dr Christopher Morris
Post: Senior Research Fellow
Dept: Child Health Group Peninsula Cerebra Research Unit for Childhood Disability Research (PenCRU)
Official Addess: University of Exeter Medical School, South Cloisters, St Luke’s Campus, Exeter, EX1 2LU
Tel: 01392 262980

Further Study Information

Current Stage:
October 2017 - August 2018
Funding source(s):
Senior Research Fellowship to Cathy Williams: NIHR £927,000 (1/10/15 for 5 years). Cerebral Visual Impairment in primary school age children: prevalence, impact and effectiveness of support

Health Area

Disease Category
Eyes & vision

Disease Name
Cerebral Visual Impairment (CVI)

Target Population

Age Range
6 - 18


Nature / type of Intervention


Consensus meeting
Delphi process
Literature review

We will first conduct a systematic review of the existing literature on outcomes used in evaluations of services or interventions for children with CVI (Aim 1)

We will then collect new data in interviews (Aim 2) to “fill in the gaps” revealed by the systematic review and capture the language and perspectives of children and their families.

Participants will be children and young people aged 6 - 18 years with a diagnosis of CVI, using any definition, and/or parents or carers of children with this diagnosis.

Sampling method
To include a range of ages and physical capabilities, maximum variation purposive sample will be used to recruit families to a matrix including younger (6-11 years old) and older (12-18 years old) children, and those with and without a diagnosis of cerebral palsy.

We will recruit children and young people from three sources initially and will use a snowballing approach to recruit more if needed. Firstly, we will ask the local Specialist teachers for Vision Impairment to post a notice with information and contact details on their website. They will also notify individuals they think might be interested. We will visit a local school for children with visual impairment (The WESC Foundation, Specialist Centre for Visual Impairment, Exeter) and distribute notices and information. Thirdly we will give the same information to a national parent support group for families of children with CVI (

Data collection – interviews
Interviews will be carried out in person, at school or at home as preferred or as convenient. Children will be interviewed on their own, after their parent has been interviewed. All interviews will be audio-recorded with consent. A topic guide based on the systematic review and comments from the advisory groups and based on approaches already reported and successful with similar-aged children will be used (for example an activity discussing “a day in the life of a child with CVI”). Interviews will be expected to take 30-45 minutes for adults and 10-30 minutes for children. When interviewing children a range of creative activities will help us to elicit views of young people about what matters most to them. We will use drawings, stories and a tablet to support these approaches to follow the topic guide.

Interviews will continue with families until the point of diminishing returns, when little or no new perspectives are forthcoming and no new outcome domains are being identified. We expect to conduct interviews with approximately 30 families in total.

A framework analysis consisting of five steps will be used. First familiarisation with the data will allow for submersion in the topic area. Secondly an initial framework will be applied by coding key issues in the transcripts. Third, the codes will be indexed into categories, fourth, thematic charts will be produced and compared by independent coders (members of the research team) and finally the charts will be interpreted into themes using key ideas and quotes from the original data.

Stakeholders Involved

Clinical experts
Consumers (caregivers)
Consumers (patients)
Patient/ support group representatives
Service providers
Service users

Study Type

COS for clinical trials or clinical research
COS for practice

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