Doctors may soon be able to detect Alzheimer’s disease long before memory loss sets in—using something as simple as a routine eye exam.

A new study suggests that subtle changes in the retina’s blood vessels could serve as an early biomarker for dementia risk.

Researchers at The Jackson Laboratory (JAX) found that twisted and narrowed vessels in the retinas of mice with a common genetic mutation strongly resemble vascular abnormalities seen in Alzheimer’s patients.

The findings build on nearly a decade of research at JAX, where scientists have linked changes in specific retinal cells to early dementia risk.

Because the retina is part of the central nervous system and shares nearly identical tissue with the brain, it provides a uniquely accessible window into neurological health.

“Your retina is essentially your brain, but it’s much more accessible,” said neuroscientist Alaina Reagan, who co-led the study with Gareth Howell, professor and Diana Davis Spencer Foundation Chair for Glaucoma Research at JAX.

“We can directly see the neurons and blood vessels, and how they behave under disease pressure.”

Retina as brain’s mirror

The team studied mice with the mutation known as MTHFR677C>T, found in up to 40% of humans. By six months of age, these mice developed twisted vessels, narrowed arteries, and reduced branching in the retina—patterns strongly associated with impaired blood flow and cognitive decline.

Such changes aren’t just localized to the eye. They mirror abnormalities previously documented in the brains of the same mice, including fewer blood vessels in the cortex and reduced cerebral blood flow. This duality underscores how vascular health in the eye may reflect systemic issues that also impact brain health.

“We can see these wavy vessels in the retinas, which can occur in people with dementia,” Reagan said. “That speaks to a more systemic problem, not just a brain- or retina-specific one.”

Mapping disease before onset

Beyond vessel abnormalities, the researchers found disrupted protein activity in both the brain and retina, pointing to problems with energy production, protein clearance, and vessel support structures. These changes may help explain how vascular dysfunction contributes to the cascade of neurodegeneration.

The study also captured the influence of sex and age. Female mice showed significantly worse outcomes: by 12 months, they had lower vessel density and fewer branches, paralleling the higher rates of dementia in women globally.

The next step is translating these findings to humans. JAX researchers are partnering with clinicians at Northern Light Acadia Hospital in Maine to explore whether similar retinal changes can be spotted during eye exams in patients carrying the mutation. If so, optometrists and ophthalmologists could help flag individuals at risk decades before cognitive symptoms appear.

“Most people over 50 have some kind of vision impairment and get checked annually,” Reagan said. “If we know which vascular signs to look for, doctors could recommend further tests and possibly intervene 20 years before cognitive decline.”

By turning the eye into a diagnostic tool for the brain, researchers hope to revolutionize how Alzheimer’s and related dementias are detected and ultimately, how they are prevented.

The study is published in Alzheimer’s & Dementia.