Collecting R from after-school today, I was greeted by an assistant who has only recently got to know R. She started to gush about her eyes, “they are so expressive; you could lose yourself in them”. And it’s true, there is something about R’s eyes that is quite captivating. Unable to reach for and grasp objects, R explores the world through her eyes. She talks with her eyes, she points with her eyes. My Mum, a retired teacher, has always maintained that, within an acceptable margin of error, the intelligence of a child can be read in their eyes. I like this idea. R is very articulate with her eyes. It has always seemed to me that there is a mismatch between R’s perceived intelligence and these captivating eyes.
Twenty years ago, when I was still a graduate student, a number of my colleagues collaborated on a project with Dr Alison Kerr. Dr Kerr, a now-retired paediatrician, was one of the first clinicians in the UK to take an interest and gain expertise in Rett Syndrome. Dr Kerr was interested in establishing how well her patients with Rett Syndrome could see.
Assessing the level of vision of someone who is unable to talk or respond in any conventional way is a non-trivial task. There are commercial tests available which have been used in patients with severe disabilities but these have all been developed primarily for infants. Older patients may refuse to engage with these tests simply because they find them too childish. Dr Kerr’s patients all refused to engage. What my colleagues did was to measure the electrical signals produced by the brain in response to some black and white check patterns using a few electrodes placed on the scalp (visual evoked potentials). These can then be used to give an estimate of how well someone can see. The results were surprising: while some of the girls and women required spectacles and one had a squint, all had good vision*. This was surprising because most neurological disorders are associated with a very high risk for poor vision. Indeed, one large scale study concluded that people with learning disability should be assumed to have visual impairment unless proven otherwise**. (Conversely, infants with visual impairment are at risk for developmental delay). For girls and women living with Rett Syndrome this is very good news and it is disappointing that this finding is not better known.
But it also raises an interesting question. If the vision of our girls is good, then the implication must be that the visual parts of the brain are relatively intact (at least at the early stages, where these simple patterns are likely to be processed). If the visual parts of the brain, which make up a large part of the cerebral cortex, are relatively intact, how much more of the brain is functioning well? Until now, the intelligence of girls like R have been difficult to test. Eye gaze technology brings the possibility of truly accessible cognitive tests tantalisingly close. I put my money on my Mum being right all along.
** van Splunder J, Stilma JS, Bernsen RMD, Evenhuis HM. Prevalence of visual impairments in adults with intellectual disabilities in the Netherlands: Cross‐sectional study. Eye 2006;20(1004‐1010)