Predicting Parkinson’s Disease Through Eye Scans : Is It Possible?

Parkinson’s disease is a complex and progressive neurological disorder that has a profound impact on the lives of millions of individuals worldwide. It primarily targets the central nervous system, unleashing a spectrum of motor and non-motor symptoms that can be physically and emotionally challenging to navigate. With over 10 million people affected globally, Parkinson’s is a significant health concern that continues to baffle researchers in their quest to unravel its precise origins and triggers.^(1,2,3)

At the core of this condition lies the gradual deterioration of specific brain cells responsible for producing dopamine, a critical neurotransmitter that plays a pivotal role in regulating movement and mood. This degeneration gives rise to the hallmark motor symptoms of Parkinson’s, including tremors, muscle rigidity, bradykinesia (sluggish movements), and difficulties with maintaining balance and posture.⁽⁴⁾

While these motor symptoms are the most recognizable aspects of the disease, Parkinson’s extends its reach beyond movement impairment. Non-motor symptoms, such as fluctuations in mood, disturbances in sleep patterns, and cognitive challenges, add layers of complexity to the condition, often impacting a person’s overall quality of life. Parkinson’s disease is a multifaceted puzzle that continues to challenge our understanding and underscores the pressing need for ongoing research and improved management strategies.^(5,6)

Since the early signs of the disease often emerge subtly, it makes it quite challenging for doctors to detect the condition at an early stage. Interestingly, one part of the body that may provide clues about Parkinson’s is the eyes. Individuals with Parkinson’s disease can encounter changes in their vision, experience dry eyes, or struggle with reading and keeping their eyes fully open.⁽⁷⁾

Recent findings from Moorfields Eye Hospital and UCL Institute of Ophthalmology have identified specific eye markers that could indicate the presence of Parkinson’s disease.⁽⁸⁾ 

Remarkably, these markers may appear approximately seven years before an official diagnosis is made. This groundbreaking study was recently published in the journal Neurology, associated with the American Academy of Neurology.⁽⁹⁾ Let us take a look at what this research shows and whether it is indeed possible to predict Parkinson’s disease through eye scans.

In the study mentioned above, a team of researchers led by Dr. Siegfried Wagner, an Honorary Clinical Senior Research Fellow at the NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology, harnessed the power of artificial intelligence to analyze data from two distinct sources — the AlzEye dataset and the U.K. Biobank database.^(10,11)

The researchers then utilized data derived from retinal eye scans acquired through optical coherence tomography (OCT).⁽¹²⁾ According to the research team, OCT is a non-invasive imaging technique capable of producing cross-sectional retinal images. In many ways, OCT functions much like ultrasound, but instead of sound waves, it employs the backscattering of light to generate high-resolution images.

Through an OCT scan, the team was able to visualize the various retinal layers and precisely measure their thickness.⁽¹³⁾ This capability proves valuable in diagnosing several medical conditions, including age-related macular degeneration, glaucoma, diabetic retinopathy, and macular holes.⁽¹⁴⁾

Upon meticulous examination of the eye scan data, the research team pinpointed disparities within two specific layers of the inner retina in individuals afflicted by Parkinson’s disease — namely, the ganglion cell-inner plexiform layer and the inner nuclear layer.⁽¹⁵⁾

The team observed thinning of the ganglion cell-inner plexiform layer in various neurological conditions, ranging from multiple sclerosis to Alzheimer’s dementia.⁽¹⁶⁾ This phenomenon may signify a broader loss of brain tissue. Notably, irregularities within the inner nuclear layer have primarily surfaced in post-mortem studies.^(17,18)

The research team found it fascinating to detect alterations in these layers, considering that cells reliant on dopamine are situated between the inner nuclear and ganglion cell-inner plexiform layers. While this is speculative, it is conceivable that the study witnessed a primary dopaminergic-related degeneration in Parkinson’s disease patients.

The researchers further established a significant correlation between the diminished thickness of both these retinal layers and a heightened risk of developing Parkinson’s disease.

The research team chose to investigate potential markers of Parkinson’s disease within eye scans due to the disease’s hallmark, which involves the depletion of cells utilizing the neurotransmitter dopamine. They also took into consideration that the eye offers a convenient gateway to the brain and is home to cells that utilize dopamine.

It is interesting to note that earlier studies have also revealed characteristics related to the loss of dopamine-producing cells in histological examinations of retinal tissue from individuals with Parkinson’s disease. However, such observations have not been consistently identified in in-vivo imaging.⁽¹⁹⁾

Leading the research team, Dr. Wagner drew caution to the fact that the research findings should be regarded as preliminary, emphasizing that they represent an early-stage discovery of an association between variances in retinal morphology and the onset of Parkinson’s disease.

There are further ongoing investigations into multimodal retinal imaging and high-dimensional modeling techniques utilizing deep learning for predicting Parkinson’s disease. Additionally, plans are also in place to explore the potential utility of retinal imaging in detecting prodromal Parkinson’s disease.⁽²⁰⁾

Upon reviewing the study, Dr. Daniel Truong, another noted neurologist and the medical director of The Parkinson’s and Movement Disorder Institute at MemorialCare Orange Coast Medical Center, expressed his enthusiasm for the potential of detecting Parkinson’s disease markers through eye scans up to seven years before clinical symptoms appear.

According to Dr. Truong, this concept, along with other early signs such as the loss of the sense of smell, constipation, and REM sleep behavior disorder, has the potential to unlock new avenues for early interventions. This could enable doctors to potentially change the disease’s trajectory or manage its symptoms more effectively.^{(21,22,23,24)}

The non-invasive nature of the detection method is being particularly appreciated since OCT scans of the retina are rapid, incredibly detailed, and noninvasive. They offer valuable insights not only into eye health but also broader health conditions.

Nevertheless, there are some reservations that remain with respect to the study’s implications. While these findings are encouraging, it is essential to consider how they will translate into real-world clinical practice. Questions about cost-effectiveness, accessibility, and the psychological impact of predicting Parkinson’s on healthy individuals also need to be addressed.

Not all medical experts, though, had the same promising view towards the results of the study. According to some experts, an OCT scan cannot definitively inform you if you currently have or will develop Parkinson’s disease.

Furthermore, there are many other conditions, apart from Parkinson’s disease, can lead to thinning of the ganglion cell layer and other retinal layers. Thin retinal layers can be associated with glaucoma, macular degeneration, retinal vascular disease, and several other conditions. At the same time, even nearsightedness can cause thinning of the ganglion cell layer, making it a non-specific finding.⁽²⁵⁾

However, the value of identifying ophthalmic signs of Parkinson’s disease during a clinical examination cannot be ignored. It is important to note that individuals with Parkinson’s disease often tend to experience a higher incidence of dry eye due to reduced blink rates. They may also encounter reading difficulties because Parkinson’s can affect their eye movements, and some people may even present with double vision. Therefore, a thorough clinical examination by an ophthalmologist or neuro-ophthalmologist can definitely help detect early signs consistent with Parkinson’s disease.

There is no doubt that the potential of predicting Parkinson’s disease through eye scans is a fascinating avenue of research. However, it is crucial to approach these findings with a measured perspective. While the study hints at a connection between retinal changes and Parkinson’s, it is not yet a reliable diagnostic tool for individual risk assessment. Thinning of retinal layers, as observed, can be linked to various conditions, making it a non-specific marker. Clinical examinations by specialists like ophthalmologists and neuro-ophthalmologists remain essential for detecting early signs of Parkinson’s.

The study opens a hopeful path for early interventions and improved disease management. Yet, extensive research and clinical validation are needed before eye scans can become definitive predictive tools. As we delve deeper into the intricate links between the eyes and the brain, the quest to understand and combat Parkinson’s disease remains promising but requires evidence-based progress.

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Also Read:

• Parkinson’s Disease: Causes, Symptoms, Investigations, Treatment
• What Are The Five Stages Of Parkinson’s Disease?
• Who May Be Trapped with Parkinson’s Disease?
• Can You Reverse Parkinson’s Disease?
• What are the Motor Symptoms of Parkinson’s Disease?
• Can Physical Therapy Help Parkinson’s Disease?
• Is Green Tea Good For Parkinson’s Disease?