Innovation

Parkinson's Early Diagnosis: Simple Eye Test Spots Changes In Retina Cells Before Symptoms Appear

Hand tremors, muscle stiffness, and impaired speech are the tell-tale signs of Parkinson's disease. The life-changing condition requires long-term treatment to help patients do simple everyday tasks. Researchers at the University College London (UCL) Institute of Ophthalmology have discovered a revolutionary eye test that may spot signs of Parkinson's before brain changes occur.

The brain changes caused by Parkinson's begin in a region that plays a role in movement. Therefore, as these changes spread, mental functions, including memory and the ability to pay attention, make sound judgments and plan steps to complete a task, become impaired. Prior to the study, doctors were only able to spot symptoms after brain cells have been damaged. Now, UCL researchers suggest the eyes, specifically the retina, could reveal the disease’s early stages.

“This is potentially a revolutionary breakthrough in the early diagnosis and treatment of one of the world’s most debilitating diseases,” said Francesca Cordeiro, lead author of the study and UCL Professor of Glaucoma & Retinal Neurodegeneration Studies, in a statement.

In the study, published in the journal Acta Neuropathologica Communications, a form of Parkinson's was induced in rats to spot potential vision changes. Cordeiro and her colleagues discovered retinal changes could be seen in the back of their eyes. Using ophthalmic instruments, retinal ganglion cell changes were found, along with alterations in thickness of the retina.

Eye A simple and non-invasive eye test may spot vision changes before Parkinson's symptoms appear. Photo courtesy of Pexels/Public Domain

Parkinson's patients are known to develop less sharp vision due to the loss of dopamine neurons in the eye's retina, according to the National Parkinson's Disease Foundation. This means there's a decreased sensitivity to contrast (color and brightness). This shortage of dopamine also damages brain cells, and is the causes of tremors, muscle stiffness, and slowness of movement and a reduced quality of life.

Cordeiro believes: “These tests mean we might be able to intervene much earlier and more effectively treat people with this devastating condition.”

Following the observation of retinal changes in rats, Cordeiro and her colleagues treated the animals with a newly formulated version of the anti-diabetic drug Rosiglitazone, which helps to protect nerve cells. After administering the drug, there was evidence of reduced retina cell death as well as a protective effect on the brain. This suggests the anti-diabetic drug could have potential as a treatment for Parkinson's.

A simple non-invasive eye test could potentially help the 60,000 Americans diagnosed with Parkinson's each year, and help narrow down the number of cases that go undetected. These treatments could revolutionize how Parkinson's is discussed and treated.

Currently, there are treatments to help lessen the severity of symptoms, but all they can do is offer symptomatic relief. Dopamine replacement therapies, like Levodopa/Carbidopa, work as Levodopa converts enzymes in the brain to produce dopamine, thereby providing a supply that has been lost as dopamine-producing neurons die due to the disease. Carbidopa works by slowing enzyme breakdown of Levodopa before it reaches the brain. This significantly improves mobility and allows patients to function relatively normally - at least in the early stages of the disease. However, it has not been shown to slow disease progression.

Cordeiro and her colleagues remain hopeful their discovery could lead to earlier treatment and slow the development of Parkinson’s.

“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”, said first author Dr. Eduardo Normando, first author of the study and Consultant Ophthalmologist at Western Eye Hospital and UCL, in a statement.

Source: Normando EM, Davis BM, De Groef L et al. 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. Acta Neuropathologica Communications. 2016.

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