Research has suggested that Parkinson’s disease can be picked up in eye scans seven years before patients report symptoms to their doctor, a disease with which about one in 37 people will be diagnosed in their lifetime.
The Telegraph reports that post-mortem examinations had already shown that Parkinson’s patients had thinner cell layers in some parts of the retina at the time of death, but it was unknown whether it was linked to the disease.
To find out, scientists at University College London (UCL) used artificial intelligence to analyse hundreds of thousands of eye scans from the Moorfield Hospitals AlzEye database, and the UK Biobank.
They discovered that in Parkinson’s patients, two layers of cells in the eye – the inner nuclear layer and the ganglion cell–inner plexiform layer – were significantly thinner.
As the cell layers diminished, the risk of developing Parkison’s increased, the team found.
And the changes could be seen up to seven years ahead of a Parkinson’s diagnosis.
A pre-screening tool
Lead author Dr Siegfried Wagner, of the UCL Institute of Ophthalmology, said: “I continue to be amazed by what we can discover through eye scans.
“While we are not yet ready to predict whether an individual will develop Parkinson’s, we hope this method could soon become a pre-screening tool for people at risk of disease.
“Finding signs of a number of diseases before symptoms emerge means that, in the future, people could have the time to make lifestyle changes to prevent some conditions arising, and clinicians could delay the onset and impact of life-changing neurodegenerative disorders.”
Doctors have known for some time that the eye can act as a “window” into the health of the rest of the body.
In recent years, a new field – known as oculomics – has emerged which seeks to spot hidden conditions through detailed scanning of the eyes.
Experts have already shown that Alzheimer’s, multiple sclerosis and schizophrenia can be spotted in eye scans, as well as a propensity for high blood pressure, cardiovascular disease including strokes, and diabetes.
High-resolution images of the retina are now a routine part of eye care widely used in clinics and opticians, and the latest study suggests a combination of scans and artificial intelligence could help find hidden health conditions which humans would miss.
Professor Alistair Denniston, consultant ophthalmologist at University Hospitals Birmingham, professor at the University of Birmingham and part of NIHR Moorfields BRC said: “This work demonstrates the potential for eye data, harnessed by the technology to pick up signs and changes too subtle for humans to see.
“We can now detect very early signs of Parkinson’s, opening up new possibilities for treatment.”
‘Intervening earlier is key’
Currently Parkinson’s is diagnosed through brain scans and symptom tests, but the breakthrough paves the way for widespread screening. Although there are currently no drugs that can prevent or reverse Parkinson’s, many trials are ongoing, and spotting the disease early may be the key to curing or ameliorating the disease.
The research was published in the journal Neurology.
Study details
Retinal Optical Coherence Tomography Features Associated With Incident and Prevalent Parkinson Disease
Siegfried Wagner, David Romero-Bascones, Alastair Denniston, et al.
Published in Neurology on 21 August 2023
Abstract
Background and objectives
Cadaveric studies have shown disease-related neurodegeneration and other morphological abnormalities in the retina of individuals with Parkinson disease (PD), however it remains unclear whether this can be reliably detected with in vivo imaging. We investigated inner retinal anatomy, measured using optical coherence tomography (OCT), in prevalent PD and subsequently assessed the association of these markers with the development of PD using a prospective research cohort.
Methods
This cross-sectional analysis used data from two studies. For the detection of retinal markers in prevalent PD, we used data from AlzEye, a retrospective cohort of 154 830 patients aged 40 years and over attending secondary care ophthalmic hospitals in London, UK between 2008 and 2018. For the evaluation of retinal markers in incident PD, we used data from UK Biobank, a prospective population-based cohort where 67 311 volunteers aged 40-69 years were recruited between 2006 and 2010 and underwent retinal imaging. Macular retinal nerve fibre layer (mRNFL), ganglion cell-inner plexiform layer (GCIPL), and inner nuclear layer (INL) thicknesses were extracted from fovea-centred OCT. Linear mixed effects models were fitted to examine the association between prevalent PD and retinal thicknesses. Hazard ratios for the association between time to PD diagnosis and retinal thicknesses were estimated using frailty models.
Results
Within the AlzEye cohort, there were 700 individuals with prevalent PD and 105 770 controls (mean age 65.5 ± 13.5 years, 51.7% female). Individuals with prevalent PD had thinner GCIPL (-2.12 μm, 95% confidence interval: -3.17, -1.07, p = 8.2 × 10-5) and INL (-0.99 μm, 95% confidence interval: -1.52, -0.47, p = 2.1 × 10-4). The UK Biobank included 50,405 participants (mean age 56.1 ± 8.2 years, 54.7% female), of whom 53 developed PD at a mean of 2653 ± 851 days. Thinner GCIPL (hazard ratio: 0.62 per standard deviation increase, 95% confidence interval: 0.46, 0.84, p=0.002) and thinner INL (hazard ratio: 0.70, 95% confidence interval: 0.51, 0.96, p=0.026) were also associated with incident PD.
Discussion
Individuals with PD have reduced thickness of the INL and GCIPL of the retina. Involvement of these layers several years before clinical presentation highlight a potential role for retinal imaging for at-risk stratification of PD.
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