Changes in the retina of the eye may reveal the presence of Parkinson’s disease before brain changes and early symptoms appear, researchers at University College London’s Institute of Ophthalmology report. Their discovery may lead to a non-invasive and low-cost eye test to detect Parkinson’s well in advance of the tremors and muscle stiffness that characterize the disease.
The study, “The retina as an early biomarker of neurodegeneration in a rotenone-induced model of Parkinson’s disease: evidence for a neuroprotective effect of rosiglitazone in the eye and brain,” was published in the journal Acta Neuropathologica Communications.
Working with rat models of Parkinson’s disease (PD) and using routine ophthalmic instruments, the team spotted changes in the retina that, they believe, can also be perceived early in patients.
“Follow-up of this [experimental rat] model demonstrated characteristic histological neurodegenerative changes in the substantia nigra and striatum by day 60, suggesting that retinal changes precede the ‘traditional’ pathological manifestations of PD,” the researchers wrote.
If successful in future clinical trials, the method would allow for an earlier diagnosis of PD and could also be used to monitor patients’ response to treatment. It has already been tested in humans for glaucoma, and clinical trials for Alzheimer’s disease are due to start soon.
“This is potentially a revolutionary breakthrough in the early diagnosis and treatment of one of the world’s most debilitating diseases,” Professor Francesca Cordeiro, a UCL Professor of Glaucoma & Retinal Neurodegeneration Studies and the study’s leader, said in a news release. “These tests mean we might be able to intervene much earlier and more effectively treat people with this devastating condition.”
After observing retinal changes in the experimental model, researchers gave the rats a newly formulated version of rosiglitazone (brand names: Avandia, Avandamet and Avandaryl), an anti-diabetic drug that helps to protect nerve cells. The treatment was seen to result in lower retina cell death and to provide a protective brain effect, suggesting it could potentially be used in Parkinson’s patients.
“Of all treatment regimen tested, sustained release administration of liposome-encapsulated rosiglitazone proved to be the most potent therapeutic strategy, as evidenced by its significant neuroprotective effect on retinal neurons at day 20, and on nigrostriatal neurons at day 60, provided convincing evidence for its potential as a treatment for PD,” the researchers said.
Parkinson’s disease, the second most common neurodegenerative disease worldwide, is marked by dopaminergic cell death in the brain’s substantia nigra and the accumulation of Lewy bodies. Neuronal death and dysfunction have been reported in other central nervous system regions, including the retina. Disease symptoms including muscle stiffness, slow movement and tremors, which are typically manifest only after more than 70% of dopaminergic cells are lost.
UCL’s research commercialization company, UCL Business, is filing a patent for the method.