Can a simple eye exam replace costly and invasive Alzheimer’s diagnostic procedures?

Researchers are investigating whether a retinal scan done with a device such as the one above can detect signs of Alzheimer’s disease.RetiSpec

Could a simple eye exam detect signs of Alzheimer’s disease?

Researchers at Massachusetts General Hospital and Brigham and Women’s Hospital have begun a study to find out. Dr. Gad Marshall, associate professor of neurology at Harvard Medical School, is testing a special retina camera and software developed by a Canadian startup to determine whether it can identify bits of amyloid plaques in the back of the eye that may indicate Alzheimer’s.

Alzheimer’s, the most common form of dementia, can already be diagnosed with about 85 percent accuracy through positron emission tomography (PET) scans of the brain or by analyzing a sample of spinal fluid, Marshall said. But few patients get those tests; PET scans are costly and require the injection of a radioactive drug, while spinal taps involve the insertion of a needle into the spinal canal.

The retinal test by RetiSpec, a Toronto medical imaging startup, is painless and could be done in a few minutes during a visit to the eye doctor.

“I think it’s a big advantage,” said Marshall, 44, an expert on Alzheimer’s imaging tests who practices at Mass. General and Brigham and Women’s. “It would be noninvasive, safer and cheaper, and more accessible.”

Marshall plans to test the equipment at Mass. General over the next 18 months on 50 people with mild cognitive impairment and 50 people without it. The study is part of a broader five-year Alzheimer’s research project he is leading at the teaching hospitals, funded with about $2 million from the National Institutes of Health.

About 5.8 million Americans have Alzheimer’s, a number expected to soar to nearly 14 million by 2050, according to the nonprofit Chicago-based Alzheimer’s Association.

With no approved medicines to significantly slow Alzheimer’s-related memory loss and impaired thinking, drug companies have spent billions of dollars trying to develop an effective treatment. None has succeeded. In a report last year, the pharmaceutical industry said there were 146 failed efforts in the 20-year period ended in 2017.

Just last week, in a stunning announcement, Cambridge-based Biogen said it would revive a medicine for early Alzheimer’s disease that it scrapped in March. That medicine targets amyloid plaques, an approach many researchers believe has been discredited.

Even if a drug company does come up with an effective treatment, diagnosing Alzheimer’s remains challenging. Some families are never certain that that disease, rather than another form of dementia or a different illness, has caused a relative’s cognitive deterioration.

The only definitive way to diagnose Alzheimer’s is to perform an autopsy of the brain after death and examine the tissue under a microscope. Tissue from deceased patients with the disorder often features amyloid plaques — abnormal clusters of protein fragments between nerve cells — and twisted spaghetti-like proteins known as tangles.

In living patients, CT scans and magnetic resonance imaging (MRI) are sometimes performed to rule out other disorders. In most cases, doctors diagnose Alzheimer’s through a process of elimination, giving patients cognitive tests, and interviewing them and their families.

Eliav Shaked, cofounder and CEO of RetiSpec, said he was inspired to come up with a new diagnostic tool partly because Alzheimer’s killed a family friend recently at the age of 76 in Washington, D.C.

“Unfortunately, the disease took her too fast for me to even pay her a visit,” said Shaked, who is 36.

His technology relies on a process called hyperspectral imaging to identify biological markers for Alzheimer’s. In addition to bits of plaque, he said, the camera can detect changes in tiny retinal blood vessels and thinning retinal nerve fibers that suggest a propensity for the disease.

The test takes about 10 minutes and can be done by a technician. It would be done in the offices of eye doctors, whose standard retinal cameras would be modified with the addition of RetiSpec’s camera and software. If the exam turned up something worrisome, the patient’s primary care physician or neurologist would be contacted.

Several other companies are exploring the possibility of using retinal scans to detect early signs of Alzheimer’s. The Alzheimer’s Association held an international workshop in Washington, D.C., in May to discuss different potential approaches.

It typically takes up to a year to get a diagnosis of Alzheimer’s, and even then the finding is only about 75 percent accurate, according to Heather Snyder, vice president of medical science relations for the Alzheimer’s Association. She said early diagnosis is critical to ensure that individuals receive appropriate care and can plan for the future and enroll in clinical trials.

Shaked said RetiSpec is the only retinal test that doesn’t require intravenous injections or eye drops to pinpoint Alzheimer’s biomarkers.

RetiSpec’s imaging tool has been tested, with encouraging results, at the Toronto Memory Program, Canada’s largest center for Alzheimer’s drug treatment trials, and at Sheba Medical Center in Tel Aviv, Shaked said. Marshall’s study in Boston is the first test of the technology in the United States.

The 50 patients with mild cognitive impairment must be at least 55 years old, the neurologist said. Many have already sought treatment at the Memory Disorders Unit at Mass. General. The 50 patients without cognitive impairment range in age from 65 to 90.

Marshall’s project has several other components, including determining whether patients can be given a series of everyday tasks — such as using an automated teller machine, or ordering a prescription by phone — to assess whether they are showing cognitive impairment. The goal is to come up with a more sensitive and meaningful series of tests to pick up signs of Alzheimer’s.

RetiSpec was a finalist in the 2016 MassChallenge, a nonprofit accelerator for promising businesses. It has also received an investment of up to $500,000 from the nonprofit Alzheimer’s Drug Discovery Foundation, which has a program to speed the development of diagnostic tests.