People with PSP often experience problems with their vision. A very common issue is a paralysis of the eyes which prevents the person from looking downwards. This vertical gaze paralysis makes it hard to do everyday tasks that usually require looking down; such as reading, using an electronic device (e.g., phone, tablet, or computer keyboard), and cutting up food. One solution that is often recommended is to use light-bending prism glasses, shown in the top figure. These glasses bend light from the lower portion of the visual field so the person can see things they cannot look at directly. In principle this seems like an effective solution that should allow people with PSP to retain some of their independence. However, somewhat surprisingly, there is very little scientific evidence that people with PSP benefit from using prisms. Furthermore, very little is known about how and why people use prism glasses, what kind of instruction or training they are given, and what challenges or issues people with PSP experience when trying to use prisms. To try and start answering these question, Dr Ali Lane and I supervised a research project by two masters students (Dan Ford and James Ireland) in which 35 people with PSP were recruited with the help of the PSP Association to tell us about their experiences of using prism glasses.
The majority of participants (74%) had heard of prism glasses, and of these participants 76% had actually tried them. The most common source of information about prisms was a neuro-ophthalmologist (40%), followed by the PSP association (20%), and the most common source of the prisms themselves was an NHS prescription. When we asked about the kinds of things prisms helped people with the most common response was reading (37% of people), followed by eating (24%), using electronic devices (19%), and watching TV (19%). However, when we asked whether people still used the prisms only 20% of people reported persisting with them. This relatively low adherence may be related to the frequency with which people reported experiencing unpleasant side effects such as disorientation (37.5%) and double vision (19%), and practical problems with the weight and fit with existing eyewear. Overall, 43% of people agreed or strongly agreed that the found the prisms useful, but only 18.5% agreed that they liked the prisms.
The results of our survey indicate that while many people with PSP are aware of prism glasses, there is scope to improve patient knowledge of this rehabilitation aid. Furthermore, while some people find them useful for reading, eating, and using electronic devices, most people with PSP do not appear to benefit from prisms or they find them hard to use. Even those who do find them beneficial do not reliably persist with their use. It is likely that better fitting and more systematic training and practice would improve the usefulness of the prisms and reduce the negative impact of side-effects such disorientation. Indeed, there is evidence from stroke survivors with inattention that training improves adherence and outcomes of prism glasses therapy. However, no such training exists for people with PSP.
It is important to be cautious when drawing conclusions from a relatively small sample, but the findings seem to suggest that current approaches to prism therapy for PSP are, unfortunately, relatively ineffective. We believe this is likely due to a lack of reliable training advice for patients, which results from a dearth of scientific evidence about the optimal way to train people in the fitting and use of prisms for different tasks. The only way to resolve this issue is to conduct more evidence-based research that can establish the optimal way to use prism glasses for the rehabilitation of PSP. We are currently looking for ways to fund more research in the important area and would be interested in hearing from people who are considering studying for a PhD on this topic.
You can learn more about our other research into attention and memory in PSP here
I first heard about PSP as a graduate student when I read a paper describing an unusual and devastating disease characterised by paralysis of the eyes. The paper reported a striking result: people with PSP had a problem moving attention that was not experienced by people with Parkinson’s disease. At the time I was doing my doctoral research and the result seemed to have profound implications for our theoretical understanding of attention. I didn’t realise at this time was that it might also be important for the purposes of diagnosis. I was keen to explore how PSP affected attention further, but unfortunately due to the rarity of the condition we had no luck finding participants. At this point end I moved on to working with stroke survivors. However, as my career progressed I often thought about the condition, and one day happened to mention it to Dr Neil Archibald, consultant neurologist at James Cook University Hospital. He had a particular interest in PSP and was keen to collaborate. He put me in touch with the PSP Association, and together we ran a workshop with patients, carers, clinicians and academics to generate research ideas.
We’re delighted to welcome Siobhan McAteer to the lab! Siobhan arrives from Oxford, where she has just completed an MSc in Psychological Research. Her project “How do we store spatial working memories?” will examine the role of the eye movement system in spatial working memory with a view to applying resource theories of visual short-term memory (e.g. Bays & Husain, 2008) to spatial working memory. Siobhan’s research is supported by an ESRC NINEDTP doctoral scholarship and she will be 2nd supervised by Dr Anthony McGregor. Welcome (back) to Durham Siobhan!