Problems with vision are all about the eyes, right? No so. Professor Gordon Dutton, a Paediatric Opthamologist for more than 20 years and Emeritus Professor of Visual Science at Glasgow Caledonian University, shares his expertise working with children with cerebral visual impairment (CVI)…

Cerebral visual impairment (CVI) is the commonest cause of visual impairment in children in the developed world, but remains little understood. The causes are many, with impaired blood supply or oxygen delivery to the brain being the commonest, in infants, children and adults.

Not surprisingly, each affected person develops their own unique set of visual difficulties. This means that the basic visual functions, the process of recognition, and the ability to see movement, survey the scene, and give visual attention, as well as visually guide movement, need to be investigated for each affected person. This can be done by taking a thorough patient history, examination and testing.

If you’ve ever been bamboozled by an optical illusion or remember the intrigue caused by ‘the dress’ then you’ll know that you can’t always believe what you see.

How I see something in front of me – like a blue / black dress – may be completely different from how you see exactly the same item.

So, how do we see, and why is this important?

It’s not just our eyes that help us see. The incoming visual information from our eyes is processed by the brain in many ways, giving us a moment-to-moment mental picture of the ever-changing scene we deem to be our visual reality. This mental imagery depends on good clarity, contrast, brightness and stereoscopic perception (or three dimensionality), with full visual field processing. All of this is almost instantly related to the massive visual data banks in the brain’s temporal lobes, bringing about conscious recognition. It doesn’t end there though…

Our body movements are guided by the visual input from the whole of our visual field, complemented by feedback from our balance systems and muscles. The whole moving visual scene has to be immediately processed in relation to our bodies (in the posterior parietal lobes) for all this to happen, mostly without our knowing. That’s why we can run down a mountain path while appreciating the view, without tripping!

When you consider the role of the brain in all of these remarkable processes, it’s not surprising that brain injury or dysfunction at any age can lead to CVI.

Understanding how we see can help explain the impact that CVI has on children. In the run up to World Sight Day we all have a chance to learn a bit more about the many conditions which impair vision, of which CVI is one. I would recommend checking out the CVI Scotland website for more info.

Recent research has shown that up to 3.4% of mainstream primary school children can be affected. More than 80% of children with cerebral palsy and 50% of those who have had a shunt to deal with a build-up of fluid in the brain have the condition. While both stroke and dementia commonly lead to CVI in adults.

Problems with the optics of the eyes (such as refractive error and impaired visual accommodation), are common in children with CVI. That’s why health visitors, mums, GPs and the like often question or check the vision of affected children during those early years, so that any problems can be picked up and dealt with. The optometry profession is especially important in supporting these children.

Parents of children with CVI and older children and adults are all empowered by having a deep understanding of what can and cannot be seen and interpreted. My colleague Helen St Clair Tracy’s talk gives an interesting insight into how she tried to discover what her son Arran sees and experiences.

Remember that every person is different and the more we can understand about what that person sees, how they experience the world, and how we can make their experiences accessible so that they can learn, the better we can support them.