Now for the first time, researchers in the University of York's Department of Biology have established a link between a mutation which triggers Parkinson's and problems with vision in an animal model.
Scientists at York studied the impact of the most common Parkinson's-related mutation on nerve cells in the visual system of the fruit fly, Drosophila.
Using electroretinagram (ERG) technology they found a gradual loss of function in eye nerve cells with the mutant gene. The fly visual system is a useful laboratory model as it contains similar amounts of dopamine to the human eye.
However, the research team, which was supported by the University's Centre for Chronic Disease and Disorders (C2D2), found that other Parkinson's-related mutations did not affect eye nerve cell function and there was no loss of vision.
Dr Chris Elliott, who led the research, said: "This is a significant step forward as it will help to identify those people with Parkinson's who may be at greater risk of changes in their vision. It will assist clinicians to manage the condition more effectively."
"We have to get away from the idea that Parkinson's is only about movement problems. This work indicates that changes in vision may also affect people with the most common form of inherited Parkinson's," he added.
The research is published in the journal Human Molecular Genetics.