New research has found an eye test could show the first sign of dementia decades before other symptoms
Early signs of dementia could be detected in routine eye tests up to 20 years before symptoms appear, according to a new study. Opticians may be able to spot tell-tale signs of Alzheimer’s disease and other forms of the debilitating condition within the next few years just by looking into patients’ eyes, say scientists.
American researchers have linked abnormal changes in the tiny blood vessels of the retinas of mice with a common genetic mutation known to increase the risk of Alzheimer’s – the most common form of dementia. The findings, published in the journal Alzheimer’s and Dementia, build on previous work from the same team at the Maine-based Jackson Laboratory (JAX), which found similar vascular changes in the brains of mice.
The study linked abnormalities in specific retinal cells to early dementia risk, which the research team says strengthens the case that the retina is a “powerful biomarker” for Alzheimer’s and other dementias. Study co-leader Dr Alaina Reagan, a JAX neuroscientist, said: “If you’re at an optometrist or ophthalmologist appointment, and they can see odd vascular changes in your retina, that could potentially represent something that is also happening in your brain, which could be very informative for early diagnostics.”
She explained that, because the retina is part of the central nervous system, scientists often see it as an extension of the brain that shares essentially the same tissue. That’s why changes in retinal blood vessels can offer early clues about brain health and diseases such as Alzheimer’s.
Dr Reagan said: “Your retina is essentially your brain, but it’s much more accessible because your pupil is just a hole, and we can see tons of stuff. All the cells are very similar, all the neurons are quite similar, all the immune cells are quite similar, and they behave similarly under pressure if you’ve got a disease.”
The researchers studied mice with a mutation called MTHFR677C>T, which is found in up to 40% of people. They found that the mice’s retinas had twisted vessels, narrowed and swollen arteries, and less vessel branching as early as six months of age.
The team said that reflects similar changes in the brain linked to poor blood flow and increased risk of cognitive decline. Dr Reagan said vessels that appear more twisted and looped than normal can signal problems with high blood pressure, as the narrowing tissue limits nutrient and oxygen transport.
She added: “We can see these wavy vessels in the retinas, which can occur in people with dementia. That speaks to a more systemic problem, not just a brain- or retina-specific problem. It could be a blood pressure problem affecting everything.”
A study by the same group in 2022 revealed similar vascular changes in the brains of mice with the same MTHFR677C>T mutation, highlighting the link between vascular health in the retina that resembles human disease. Dr Reagan said: “These mice have fewer vessels in their cortex and reduced blood flow to their brains. These changes are subtle, but they are there.”
The researchers also discovered changes in protein patterns in both the brain and retina. They found disruptions in how cells produce energy, remove damaged proteins, and maintain the structure and support of blood vessels, offering important clues about how the MTHFR677C>T mutation affects the eye.
Dr Reagan says the findings also support a growing theory that blood vessel health plays a “central” role in neurodegenerative diseases. She said: “A lot of these molecular changes are happening in conjunction, which suggests these systems in brain and retinal tissue are working in tandem.”
Dr Reagan says that, even though more studies are needed to gain a deeper understanding of how vascular health in the retina affects the risk of dementia, the new insights have “important” implications for people with this genetic factor. For example, the study also showed the influence of sex and age, with female mice showing worse outcomes.
By 12 months, they showed reduced vessel density and branching, highlighting progressive vascular changes. Similarly, women develop dementia more often than men, according to the World Health Organisation (WHO).
To see if the link between the mutation and vascular changes occurs in humans, as well as whether the new insight could be used in eye exams, the researchers are teaming up with doctors and dementia care specialists at Northern Light Acadia Hospital in Bangor, Maine.
The idea is to learn more about how eye health adds to overall risk for dementia. Dr Reagan added: “Most people over 50 have some kind of vision impairment and get checked annually for prescription changes. Are they more at risk if they have these vascular changes, and is that a point when doctors could start mitigating brain changes?
“That could be 20 years before cognitive damage becomes noticeable to patients and their families.”