We only see the world through our own eyes. We cannot know the experience of others, and we all have our own version of normal. But what if some children are seeing their world completely differently and no-one is aware how truly different that actually is? These children have a cerebral visual impairment, which means that part of their brain that deals with vision is not working properly. Ian Hamilton, himself completely blind, investigates this little-known sight problem. He asks if our lack of understanding about vision means that some children are being misdiagnosed with autism. And are there people out there having problems with their sight that not even they know about?