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Are eyes the window to diagnosis?
As things currently stand, diagnosing Parkinson’s disease usually happens late in the disease stage, as usually symptoms only become apparent after 70 percent of the dopamine-producing cells in the brain have been lost. But a new method of diagnosis could provide confirmation much earlier—and it's as simple as an eye test.
This new diagnostic method comes out of the University College London (UCL) Institute of Ophthalmology. Researchers found that it is possible to see changes in the retina in individuals with Parkinson’s disease before changes in the brain occur or symptoms start to show. The results of this work appeared in a paper titled “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,” which was published in Acta Neuropathologica Communications.
The team was led by Prof. Francesca Cordeiro, UCL Professor of Glaucoma & Retinal Neurodegeneration Studies. The retinal changes in question can be seen with regular instruments used by optometrists. Specifically, the paper's abstract reports that the team used “longitudinal in-vivo imaging with DARC (detection of apoptosing retinal cells) and OCT (optical coherence tomography) technologies” to assess the retinas of the animal models. They found increased retinal ganglion cells apoptosis as well as “a transient swelling of the retinal layers at day 20 of the rotenone insult.” When they followed up by day 60, they saw “characteristic histological neurodegenerative changes in the substantia nigra and striatum … suggesting that retinal changes precede the 'traditional' pathological manifestations of PD.”
After seeing these changes in an experimental animal model, the researchers treated the animals with a new version of Rosiglitazone, an anti-diabetic drug that helps protect nerve cells. Following administration, they saw evidence of reduced retina cell death, as well as a protective effect on the brain.
“Our results demonstrate significant retinal changes occurring in this model of PD. We show that rosiglitazone can efficiently protect retinal neurons from the rotenone insult, and that systemic administration of liposome-encapsulated rosiglitazone has an enhanced neuroprotective effect on the retina and CNS (Central Nervous System). To our knowledge, this is the first in vivo evidence of RGCs loss and early retinal thickness alterations in a PD model.”
“These discoveries have the potential to limit and perhaps eliminate the suffering of thousands of patients if we are able to diagnose early and to treat with this new formulation,” said first author Dr. Eduardo Normando, consultant ophthalmologist at Western Eye Hospital and UCL. “The evidence we have strongly suggests that we might be able to intervene much earlier and more effectively in treating people with this devastating condition, using this non-invasive and affordable imaging technique.”
Parkinson’s disease is the second most common neurodegenerative disease worldwide, after Alzheimer’s disease, with one in 500 people affected. The destruction of dopamine-producing cells leads to tremors and often a decrease or loss of autonomous motor control.
In addition to this work in Parkinson’s disease, this approach has also been tested in humans with glaucoma, and trials are expected to begin soon for Alzheimer’s disease as well.
SOURCE: UCL press release