A simple eye test can quickly detect the early signs of a rare type of dementia, a new study found.
The thinning of the outer retina indicates the patient has frontotemporal dementia, an uncommon type of dementia that mainly affects the front and sides of the brain.
It is hard to diagnose because it does not initially cause memory problems and like other types of dementia, it tends to develop slowly and get gradually worse over several years.
It affects around 16,300 people or two per cent of all dementia cases and signs include personality and behaviour changes and problems with language, mental abilities and memory.
Sufferers may also experience physical problems, such as slow or stiff movements, loss of bladder or bowel control, muscle weakness or difficulty swallowing.
There is no single test and it is among the most common causes of midlife dementia.
But it is often misdiagnosed as Alzheimer’s or vice versa.
Currently diagnosis is based on an assessment of symptoms and mental abilities, blood tests to rule out conditions with similar symptoms, brain scans and testing spinal fluid to rule out Alzheimer’s.
Now scientists at the University of Pennsylvania School of Medicine have found eye changes may signal frontotemporal dementia, also known as frontotemporal lobe degeneration - FTD.
A simple eye exam and retinal imaging test improves the accuracy of a diagnosis by detecting a thinning of the outer retina - the layers with the photoreceptors through which we see.
The retina is potentially affected by neurodegenerative disorders because it is a projection of the brain.
Previous studies suggested those with Alzheimer’s and motor neurone disease also have thinning of the retina in a different part of the retina.
Lead author Assistant Professor of Ophthalmology Dr Benjamin Kim said: “Our finding of outer retina thinning in this carefully designed study suggests that specific brain pathologies may be mirrored by specific retinal abnormalities.”
Senior author Professor of Neurology Dr Murray Grossman added: “As we enter an era of disease-modifying treatments for neurodegenerative disorders, it is essential for us to have tools that can identify the specific pathologies accumulating in the brain so that we can administer the appropriate treatments to patients who are likely to benefit.”
The study looked at 38 FTD patients and 44 who did not have any neurodegenerative disease.
The FTD patients were carefully characterised with clinical exams, cerebrospinal fluid biomarkers to exclude Alzheimer’s Disease, and genetic testing.
Researchers then employed an eye-imaging technology called spectral-domain optical coherence tomography (SD-OCT), which uses a safe light beam to image tissue with micron-level resolution. SD-OCT imaging is inexpensive, non-invasive, and quick.
Measurements of the retinal layers showed that the outer retinas of the FTD patients were thinner than those in the control subjects.
This relative thinning of outer retinas was caused by a thinning of two specific portions of the outer retina, the outer nuclear layer (ONL) and ellipsoid zone (EZ).
The ONL of FTD patients was about 10 per cent thinner than controls, and this ONL thinning was the primary source of the outer retina thinning.
The degree of retinal thinning among FTD patients also had a significant tendency to be worse when the patients’ scores on a standard cognition test were lower.
Previous studies found a loss of optic nerve fibres and associated thinning of the inner retina in a few other neurodegenerative disorders including Alzheimer’s, motor neurone, and Lewy-body dementia.
The results suggested FTD manifests in a different way in the structures of the retina, and this difference, detectable with a retinal imaging test, might help doctors distinguish one disorder from another.
And FTD is not a single disorder but rather a grouping of distinct disorders so retina imaging can distinguish the different sub types.
Some FTD subtypes involve the abnormal accumulation, in affected brain areas, of thread-like aggregates of a protein called tau.
Other FTD subtypes feature abnormal aggregates of a protein called TDP-43.
They observed that the outer retinal thinning seemed to occur chiefly in the probable-tau pathology group.
They grouped the participants into probable-tau, probable-TDP-43, and unknown pathology categories and found the outer retinal thinning seemed to occur chiefly in the probable-tau pathology group Prof Kim concluded: “Prior studies have suggested that tau is expressed in photoreceptor cells, and so we hypothesised that patients with tau brain pathology may have photoreceptor abnormalities.
“It was exciting to acquire data that appear to confirm our hypothesis.”
The study was published in Neurology.
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules hereLast Updated:
Report this comment Cancel