The eyes have it

DSC_0159Collecting 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.

 

*Saunders, K. J., McCulloch, D. L. and Kerr, A. M. (1995), Visual function in Rett Syndrome. Developmental Medicine & Child Neurology, 37: 496–504. doi: 10.1111/j.1469-8749.1995.tb12037.x

** van
Splunder
J, 
Stilma
JS,
 Bernsen
RMD,
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HM.
Prevalence
 of
 visual
impairments
 in 
adults
with
 intellectual
 disabilities
 in 
the 
Netherlands: 
Cross‐sectional
 study.
Eye
 2006;20(1004‐1010)

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2 thoughts on “The eyes have it

  1. As one of the researchers working with the lovely Dr Kerr on the paper you cite, I am sorry that we didn’t catch on better to the reasons for the girls lack of engagement with the eye movement test of vision; especially as their parents all told us that they used their eyes to make choices at home. I distinctly remember we were told by parents that the girls used eye movements to indicate what they wanted to eat and that junk food was very motivating (sounds like R from what you’ve said about Pringles!). I think as researchers we just thought the girls weren’t able to produce appropriate eye movements even though we realised they could see the targets. Your blog posts are beautifully written, insightful, thought provoking and informative and have brought back to mind the special girls and their families that we met all those years ago. I look forward to the next one…. and I’m so glad R’s new teacher is receptive to your suggestions and to R’s thirst to learn.

  2. Thanks for the kind words Kathryn. I am reminded of an anecdote that a clinician told us soon after R’s diagnosis. She said that a study had looked to see whether girls with Rett could unscramble a simple 4 piece jigsaw puzzle of a clown. The younger girls managed this easily but the older girls that they tested seemed unable to do the task. Some bright spark had the idea to replace the clown with a picture of Colin Firth … and the older girls all managed the task easily!

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