Eye test may detect early retinal changes in Parkinson’s: Study
Tracking changes in eye layer may help in diagnosing disease sooner
Parkinson’s disease can lead to early retinal changes — alterations in the thin layer at the back of the eye, known as the retina, that’s responsible for detecting light and sending visual signals to the brain — that can be revealed with the use of a simple eye test, a study has found.
According to the researchers, these retinal changes can be detected using electroretinography, a noninvasive test that measures how well the retina responds to light and transmits signals to the brain.
“These changes offer a promising avenue for diagnostic exploration, especially within the eye, which has been proposed as a ‘window to the brain,’” the researchers wrote
The new findings add to earlier evidence that Parkinson’s can make the retina thinner and less readily responsive to light. Tracking these changes could help diagnose the disease sooner and thus allow clinicians to start treatment earlier, when it’s likely to be most effective, per the team.
The study, “Early detection of Parkinson’s disease: Retinal functional impairments as potential biomarkers,” was published in the journal Neurobiology of Disease.
Retinal changes detected using noninvasive test called electroretinography
Parkinson’s is diagnosed based on the presence of slowness of movement, known medically as bradykinesia, and one or more of three other motor symptoms — resting tremor or shaking, stiffness or rigidity, and problems with balance. However, there is increasing evidence of brain changes occurring years before such motor symptoms manifest.
Most people with Parkinson’s develop early problems with vision, such as blurred vision. These problems are related to the death of nerve cells in the retina, where light is sensed and converted into electrical signals that are sent to the brain.
Now, a team of researchers from Canada used electroretinography to look for changes in the eye’s retina that may reflect alterations in the brain. For this test, a doctor begins by putting numbing drops in the patient’s eyes. An electrode is then placed on each eye to measure the electrical activity of the retina in response to light.
Retinal functional impairments can be detected early in the progression of Parkinson’s disease, particularly among females. … [Electroretinography shows] promise in facilitating early diagnosis, disease monitoring, therapeutic intervention, and ultimately enhancing patient outcomes.
To model the disease, the researchers used mice that produced a faulty version of human alpha-synuclein linked to familial Parkinson’s. In Parkinson’s, faulty alpha-synuclein proteins build up as toxic clumps that cause the death of dopaminergic neurons. These nerve cells produce dopamine, a chemical signal that is needed for motor control.
Compared with the retina of healthy mice, that of the Parkinson’s mice showed reduced response to light at two and four months. This was especially true in female animals. Analysis of the retina under a microscope suggested that loss of function was likely due to alpha-synuclein buildup in the retina.
The study also compared electroretinography data from 20 adults with idiopathic Parkinson’s — where the disease is due to an unknown cause — and 20 age-matched healthy adults. On average, the Parkinson’s patients had been living with the disease for 4.15 years, and their average Hoehn and Yahr score was 2.07, indicating motor symptoms on both sides of the body without balance issues.
The results showed that women with Parkinson’s had a reduced response to light, with amacrine cells — a type of nerve cell found in the retina that’s key for processing visual information — exhibiting weaker activity. These findings suggest that Parkinson’s may impact vision differently in women, according to the researchers.
“Retinal functional impairments can be detected early in the progression of Parkinson’s disease, particularly among females,” the researchers wrote, noting that “electroretinography detects early retinal anomalies in Parkinson’s.”
The team concluded that this eye test “[shows] promise in facilitating early diagnosis, disease monitoring, therapeutic intervention, and ultimately enhancing patient outcomes.”
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