A novel imaging device has been created by biomedical engineers at Duke University that could be used in a non-invasive diagnostic test for Alzheimer’s disease. The device allows researchers to measure the thickness and texture of different layers of the retina, changes to which are caused by Alzheimer’s disease.
The search is currently on for a biomarker for Alzheimer’s disease that can be easily detected in patients, preferably individuals who are not yet exhibiting symptoms of Alzheimer’s disease. There is currently no cure for Alzheimer’s disease, the most common cause of dementia, but early interventions such as mental exercises and drugs can help to slow the progression of the disease and improve quality of life for patients. Currently, Alzheimer’s disease is usually diagnosed when patients are experiencing cognitive decline. A diagnosis is usually made with a PET or MRI scan. By the time a diagnosis is made, the disease is often in the advanced stages when interventions are less likely to be effective.
Studies have shown that patients with Alzheimer’s disease exhibit changes in the retina. The retina is an extension of the brain and scans of the retina could be used as an alternative test to determine if a patient has the disease. Patients with Alzheimer’s disease often have structural changes in the retina, such as the thinning of the inner layers of the retina at the back of the eye. Any thinning of these retinal layers could indicate a decrease in neural tissue.
A retinal scan would be non-invasive and could be conducted on patients who are not exhibiting any symptoms of Alzheimer’s disease. The scan could be performed in a doctor’s surgery, during an eye test and examination along with tests for glaucoma, or even at a pharmacy. The test would be easy to administer and could be conducted at a very low cost to the patient.
The imaging device developed by the Duke University researchers was tested in a mouse model of Alzheimer’s disease. The researchers report statistically significant thinning of the nerve fiber layer in AD mouse retinas compared to wild type (WT) age-matched controls.
Thinning of the retina alone will not allow Alzheimer’s disease to be diagnosed, as several other diseases can cause a thinning of the retina, such as glaucoma and Parkinson’s disease. The optical coherence tomography (OCT) devices currently used to detect thinning of the retina may therefore produce inconsistent results.
“Previous research has seen a thinning of the retina in Alzheimer’s patients, but by adding a light-scattering technique to the measurement, we’ve found that the retinal nerve fiber layer is also rougher and more disordered,” said Adam Wax, PhD, professor of biomedical engineering at Duke University. Combining data on changes in the thickness of the retina with changes in the structure of the neurons could help to differentiate retinal changes caused by Alzheimer’s disease and changes caused by other diseases.
“Our new approach can measure the roughness or texture of the nerve fiber layer of the inner retina,” said Ge Song, graduate researcher at Duke University. “It can provide a quick and direct way to measure structural changes caused by Alzheimer’s, which has great potential as a biomarker of the disease.”
Current OCT devices are expensive, costing up to $120,000. The device developed by Wax weighs around 4lbs, is around the size of a lunchbox, and is far less expensive. Wax believes the device could be purchased for around $15,000.
You can read more about the study in the paper – Multimodal Coherent Imaging of Retinal Biomarkers of Alzheimer’s Disease in a Mouse Model – was recently published in Scientific Reports. DOI: 10.1038/s41598-020-64827-2