Diagnostic overshadowing is not a term which makes it into the mainstream media very often. It refers to a tendency to attribute all of a patient’s problems to a major condition, thereby allowing other co-existing conditions go undiagnosed.
It is a particular problem for people with learning disabilities, who often find health professionals make assumptions that their behaviour is a part of their disability without exploring other factors such as biological determinants.
This is an area which has interested Kathryn Saunders, professor of optometry and vision science at Ulster University, for many years. Prof Saunders has led pioneering research addressing a significant knowledge gap in understanding myopia prevalence amongst children with a developmental disability. Her work has had significant impact in developing public health information relating to myopia and securing commitment for enhanced eye-care services for children in special education settings in England.
“This is an area of research I’ve been involved in for over 30 years,” she says. “Everyone is interested in myopia but research into children with disabilities is less sexy and less interesting for people. But the difference you can make to people’s lives and families is just unbelievable. It’s something I’m very passionate about.”
Part of the problem is that we expect children to tell us if they can’t see something properly. “Children with learning disabilities have different ways of communicating or may not communicate at all,” Saunders explains. “If the child doesn’t see the difference between a horse and a cow it can be put down to their learning disability rather than a sight defect. People have low expectations of the children and the problems are attributed to their underlying disability, whereas the child may have difficulty seeing colours, focusing and so on. This results in diagnostic overshadowing and it’s a very big problem for children with learning disabilities.”
Associated vision problems
The issue is compounded by the fact that many conditions have associated vision problems. “You have to know what’s normal for the particular condition. I have concentrated on Down syndrome, autism and cerebral palsy. The brain is a huge part of how we see the world.”
The scale of the problem is highlighted by research carried out by UK charity SeeAbility, which found children in special schools in England are 28 times more likely to have problems with their vision and a six-year-old child with Down syndrome is 10 times more likely to have a sight defect.
It’s not as simple as carrying out normal eye tests, however. “Think about a child with learning disabilities and what they see when an optometrist comes up to them with a shining bright light in a dark room – it’s quite frightening.”
Saunders’ own research has led to significant progress in the area. The Special Education Eyecare (SEE) project, which was funded by Action Medical Research, saw a comprehensive eye-care service being provided in a special school in England to establish if it resulted in a measurable benefit.
“A school is a very good setting for eye tests,” Saunders says. “You can do part of the test in the morning and finish it in the afternoon, so it is not overwhelming for the child.”
The results, which showed clear benefits, were published in a research paper last year. The outcomes included an improvement in visual status, with more children having their visual problems managed properly and an improvement in classroom engagement. Another benefit saw parents and teachers reporting value from the in-school service and from the reports and advice they received from the eye-care professionals on each child’s visual status and visual needs.
“They not only understood the lay description of the vision information but used this information to help the child at home and in the classroom,” says Saunders.
“NHS England have used the outcomes from the SEE project in their design and implementation of a new, evidence-based in-school eye-care programme which will reach over 100,000 children each year,” she adds. “We are working with the Public Health Agency and the Health and Social Care Board in Northern Ireland to do something similar.”
Her research has also addressed testing difficulties. “I did my PhD in the University of Cardiff with Maggie Woodhouse, who is a pioneer in this area. We wanted to find a way to measure focus in an objective way.”
Commercially available tool
This resulted in the development of the Ulster-Cardiff Accommodation Rule (or UC-Cube), the first commercially available tool that allows rapid, clinical assessment of focusing accuracy without the need for the patient to communicate.
The UC-Cube is a unique tool providing a standardised stimulus and measurement framework within which to conduct dynamic retinoscopy, objectively measure focusing ability and contextualise outputs against research-derived normative data.
“We started out by getting the technicians in the universities to make it for us but then Maggie and I put our heads together to make it commercially available,” says Saunders. “All the child has to do is look at an illuminated picture and the device does the rest. It can even be used with tiny babies.”
The UC-Cube is now used in countries across the world, including Australia, Sweden, South Africa, Antigua, India and the United States, with users confirming benefits to patients and clinical practice.
The next step will be to take the testing out of the special school setting. “Once we have comprehensive eye-care services up and running in special schools, we will try to prove if it works for children in mainstream schools. More and more children with learning disabilities are being educated in mainstream settings.”