Alzheimer's eyes

Eyes reveal early Alzheimer's disease

Reduced blood capillaries are new way to diagnose early cognitive impairment

April 5, 2019

Science Daily/Northwestern Universit

Reduced blood capillaries in the back of the eye may be a new, noninvasive way to diagnose early cognitive impairment, the precursor to Alzheimer's disease in which individuals become forgetful, reports a newly published Northwestern Medicine study.

 

Scientists detected these vascular changes in the human eye non-invasively, with an infrared camera and without the need for dyes or expensive MRI scanners. The back of the eye is optically accessible to a new type of technology (OCT angiography) that can quantify capillary changes in great detail and with unparalleled resolution, making the eye an ideal mirror for what is going on in the brain.

 

"Once our results are validated, this approach could potentially provide an additional type of biomarker to identify individuals at high risk of progressing to Alzheimer's," said Dr. Amani Fawzi, a professor of ophthalmology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician. "These individuals can then be followed more closely and could be prime candidates for new therapies aimed at slowing down the progression of the disease or preventing the onset of the dementia associated with Alzheimer's."

 

Therapies for Alzheimer's are more effective if they are started before extensive brain damage and cognitive decline have occurred, added Fawzi, the Cyrus Tang and Lee Jampol Professor of Ophthalmology.

 

The study was published April 2 in PLOS ONE.

 

It's known that patients with Alzheimer's have decreased retinal blood flow and vessel density but it had not been known if these changes are also present in individuals with early Alzheimer's or forgetful mild cognitive impairment who have a higher risk for progressing to dementia.

 

Multicenter trials could be implemented using this simple technology in Alzheimer's clinics. Larger datasets will be important to validate the marker as well as find the best algorithm and combination of tests that will detect high-risk subjects, said Sandra Weintraub, a co-author and professor of neurology and of psychiatry and behavioral sciences at Feinberg.

 

Weintraub and her team at the Northwestern Mesulam Center for Cognitive Neurology and Alzheimer's Disease recruited 32 participants who had cognitive testing consistent with the forgetful type of cognitive impairment, and age-, gender- and race- matched them to subjects who tested as cognitively normal for their age. All individuals underwent the eye imaging with OCT angiography. The data were analyzed to identify whether the vascular capillaries in the back of the eye were different between the two groups of individuals.

 

Now the team hopes to correlate these findings with other more standard (but also more invasive) types of Alzheimer's biomarkers as well as explore the longitudinal changes in the eye parameters in these subjects.

 

"Ideally the retinal findings would correlate well with other brain biomarkers," Fawzi said. "Long-term studies are also important to see if the retinal capillaries will change more dramatically in those who progressively decline and develop Alzheimer's dementia."

https://www.sciencedaily.com/releases/2019/04/190405124247.htm

Could an eye doctor diagnose Alzheimer's before you have symptoms?

Study suggests loss of blood vessels in retina reflect changes in brain health

March 11, 2019

Science Daily/Duke University Medical Center

A study of more than 200 people suggests the loss of blood vessels in the retina could signal Alzheimer's disease.

 

A study of more than 200 people at the Duke Eye Center publishing March 11 in the journal Ophthalmology Retina suggests the loss of blood vessels in the retina could signal Alzheimer's disease.

 

In people with healthy brains, microscopic blood vessels form a dense web at the back of the eye inside the retina, as seen in 133 participants in a control group.

 

In the eyes of 39 people with Alzheimer's disease, that web was less dense and even sparse in places. The differences in density were statistically significant after researchers controlled for factors including age, sex, and level of education, said Duke ophthalmologist and retinal surgeon Sharon Fekrat, M.D., the study's senior author.

 

"We're measuring blood vessels that can't be seen during a regular eye exam and we're doing that with relatively new noninvasive technology that takes high-resolution images of very small blood vessels within the retina in just a few minutes," she said. "It's possible that these changes in blood vessel density in the retina could mirror what's going on in the tiny blood vessels in the brain, perhaps before we are able to detect any changes in cognition."

 

The study found differences in the retinas of those with Alzheimer's disease when compared to healthy people and to those with mild cognitive impairment, often a precursor to Alzheimer's disease.

 

With nearly 6 million Americans living with Alzheimer's disease and no viable treatments or noninvasive tools for early diagnosis, its burden on families and the economy is heavy. Scientists at Duke Eye Center and beyond have studied other changes in the retina that could signal trouble upstream in the brain, such as thinning of some of the retinal nerve layers.

 

"We know that there are changes that occur in the brain in the small blood vessels in people with Alzheimer's disease, and because the retina is an extension of the brain, we wanted to investigate whether these changes could be detected in the retina using a new technology that is less invasive and easy to obtain," said Dilraj S. Grewal, M.D., a Duke ophthalmologist and retinal surgeon and a lead author on the study. The Duke study used a noninvasive technology called optical coherence tomography angiography (OCTA). OCTA machines use light waves that reveal blood flow in every layer of the retina.

 

An OCTA scan could even reveal changes in tiny capillaries -- most less than half the width of a human hair -- before blood vessel changes show up on a brain scan such as an MRI or cerebral angiogram, which highlight only larger blood vessels. Such techniques to study the brain are invasive and costly.

 

"Ultimately, the goal would be to use this technology to detect Alzheimer's early, before symptoms of memory loss are evident, and be able to monitor these changes over time in participants of clinical trials studying new Alzheimer's treatments," Fekrat said.

https://www.sciencedaily.com/releases/2019/03/190311090958.htm

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