Fast, affordable Alzheimer's detection? Scientists are developing eye tests that could one day detect the hallmarks of Alzheimer’s and mild cognitive impairment, from amyloid plaques to vascular disease.
Right now, a definitive Alzheimer’s diagnosis can only be obtained through the detection of beta-amyloid levels in the brain — clumps of a protein associated with progressive cell death and cognitive impairment — through an expensive and highly specialized brain scan or a lumbar puncture to sample the fluid that bathes the brain and spinal cord. The former is seldom covered by Medicare and only available in certain hospitals. The latter is just uncomfortable — not to mention it requires specialists and special equipment. The good news? Easier ways of diagnosing early-stage Alzheimer’s are in the works.
There are, for example, several amyloid blood tests designed to detect Alzheimer’s, some of which are already in use. These are easier to administer, easier to find, and more affordable than the existing go-to’s. Some are even being designed to be administered at home. The problem here is, the tests aren’t covered by most insurance providers. So far, they are not widely used — nor widely trusted by doctors — to definitively diagnose Alzheimer’s disease. This isn’t the only other option in play, however. Researchers are also well on their way to repurposing diagnostic tests already in use for other conditions, hoping to apply those to Alzheimer’s disease. Some are as simple as a scan of one’s eye.
Alzheimer’s disease, it turns out, doesn’t just affect the brain, and leave clues in the blood. It also affects the retina in the eye, in ways that scientists say are visible some 20 to 30 years before Alzheimer’s cognitive symptoms begin to appear. Millions of Americans receive routine retinal scans every year. Neuroimmunology and neuro-ophthalmology expert Maya Koronyo-Hamaoui says that adding in a few more tests (and a few more minutes) to the appointment could make detecting Alzheimer’s fast and affordable.
Koronyo-Hamaoui, a professor at Cedars-Sinai Medical Center, is currently developing retinal scans for Alzheimer’s disease. “The retina is the only central nervous system organ not shielded bone that can be imaged directly and repeatedly,” she told Being Patient.
How will much retinal tests for Alzheimer’s cost?
According to Koronyo-Hamaoui, in the future, a modified version of the standard eye exam could detect the earliest stages of Alzheimer’s disease. These new techniques and additions aren’t very expensive, she said.
Depending on location, a comprehensive eye exam involving all these tests may cost between $50 to $250. Many of the retinal tests and scans used today could be repurposed for Alzheimer’s. This would require more training for eye doctors, which would allow them to recognize the signs of Alzheimer’s alongside other eye diseases that they already diagnose.
“These will give you a really high resolution look at small blood vessel changes that are known to be defective in Alzheimer’s disease,” Koronyo-Hamaoui said.
- Fundus imaging. This test takes a picture of the back-surface of the eye.
- Retinal imaging. This test takes a picture of the retina which is home to many of the eye’s nerve cells.
- Optical coherence tomography. A technique used to take pictures of different layers of the eye.
- An eye drop to visualize beta-amyloid plaques Koronyo-Hamaoui’s lab developed curcumin eye drops that also allow doctors to visualize beta-amyloid plaques. Curcumin, the active ingredient in the turmeric spice, happens to stick to beta-amyloid proteins. Shining a special light into the eye renders the beta-amyloid proteins bound to curcumin visible. This makes it possible for doctors (or artificial intelligence algorithms) to count the amount of plaques and track their progression. It is estimated that using curcumin eye drops to detect beta-amyloid plaques would cost $285 per test.
- AI algorithms Software and computer programs could help doctors and technicians detect Alzheimer’s from routine scans taken during an eye exam. The images from the eye exam could be fed into a program that will predict whether someone is likely to have beta-amyloid plaques in their brain.
“AI will help tremendously,” Koronyo-Hamaoui. “It can analyze 1000s of images and spot the signs that are specific for this condition.”
A Lancet Digital Health 2022 publication, researchers shared an AI algorithm they developed that could determine whether someone was beta-amyloid positive from a retinal image correctly 80 percent of the time. As scientists learn more about how Alzheimer’s affects the retina, it may be possible to develop better algorithms.
Researchers believe that AI algorithms would cut diagnostic costs while making the process faster and more efficient. However, it isn’t clear how much these algorithms would affect the cost of standard eye exams.
New types of retinal scans for Alzheimer’s
Another option for detecting Alzheimer’s disease requires the development of new retinal scanners. Some scientists are using a technique called hyperspectral imaging to capture how visible and non-visible light bounces off the retina. Beta-amyloid plaques have a unique signature that is visible using this kind of imaging.
Although a hyperspectral camera is a specialized piece of equipment that can cost more than $10,000 researchers have developed versions of this camera that cost only $800. This makes hyperspectral imaging another low-cost diagnostic option.
When will retinal diagnostics be available?
It isn’t really clear when these new diagnostics will hit the market. Koronyo-Hamaoui said that the timeline would be “hard to predict”. While many people donate their brains to science after they die, few make the same consideration for their eyes. Scientists need both to cross-reference the changes in the retina with the brain.
It is hard to develop a small device capable of simultaneously measuring many different biomarkers of Alzheimer’s. Even if developed, the other problem is analyzing the results quickly and accurately. Solving these challenges will lead to the development of affordable and accessible retinal scans to catch Alzheimer’s early in its tracks. That means an early diagnosis, more time to get treatment or enroll in clinical trials, and potentially more time to spend with loved ones.