Vision tests predict cognitive decline linked to Parkinson's

Scientists in the UK have uncovered evidence that simple vision tests can predict who will develop Parkinson's dementia. And the evidence shows that a loss of wiring in the brain may be the cause. 

New research, by a team at University College London (UCL), adds to evidence that vision changes come before the cognitive decline that occurs in many, but not all, people with Parkinson's. 

The evidence also shows that the cause of the vision changes may be due to a loss of connections and a change in chemical signalling in the brain.

The team suggests these findings may help researchers identify people at risk and tackle the decline before it's too late.

Connections in the brain

In a healthy brain, there are strong connections between different areas of the brain. 

Although the connections vary between different brain areas, a loss of connections could be linked to problems with how the brain works.

What the researchers did

The London-based team published 2 related studies. The first, published in Communications Biology, showed that people with Parkinson's have more lost connections across the whole brain than people without the condition.

This study also highlights that visual problems are linked to changes in particular areas of the brain, including memory-related regions in the temporal lobe. And people at risk of cognitive decline showed changes in chemical messengers in the brain, including acetylcholine, serotonin and noradrenaline.

The second study, published in Movement Disorders, looked specifically at these visual problems. The team showed that a vision test involving commonly used eye charts and distorted images of cats and dogs could predict who would develop dementia after 18 months. 

In people who developed Parkinson's dementia, the team also identified reduced connections between areas of the brain, including in areas relating to vision and memory. Changes that can only be seen because of new developments that are helping researchers analyse brain scans in much greater detail.

Dr Beckie Port, Research Communications Manager at Parkinson's UK, comments:

"One of the most challenging aspects of Parkinson's, for both people affected by the condition and researchers working towards new treatments, is how it affects people in such different ways. 

"Having a simple test to identify who is at risk of developing Parkinson's dementia can help people plan for the future and also aid the discovery of treatments that specifically target this symptom. This in itself is a massively exciting prospect. But perhaps even more impressive is the discovery of measurable changes in the wiring of the brain, which are believed to be linked to why these symptoms appear.

"This is hugely important as it may provide a missing tool needed to see what treatments can actually stop the changes in the brain caused by Parkinson's."

Memory, thinking problems and dementia in Parkinson's

There are 2 main types of dementia that affect some people with Parkinson's. They are called Parkinson's dementia and dementia with Lewy bodies.