In a new study, researchers have devised a new imaging device capable of measuring both the thickness and texture of the various layers of the retina at the back of the eye.
The advance could be used to detect a biomarker of Alzheimer’s disease, potentially offering a widespread early detection tool for the disease.
The research was conducted by a team at Duke University.
Diagnoses of Alzheimer’s disease are currently only made after a patient begins to show symptoms of cognitive decline.
Even then, the only way to definitively determine that Alzheimer’s was the cause is with expensive MRI and PET scans or through an autopsy.
But if disease progress can be halted through early interventions such as drugs and mental exercise, patients can have a greatly improved quality of life. This is why researchers are looking for biomarkers that could be used as early warning signs of the disease.
One such potential biomarker comes from the retina, which is literally an extension of the brain and part of the central nervous system.
Previous research has shown that Alzheimer’s can cause structural changes to the retina, most notably a thinning of the inner retinal layers.
Other diseases such as glaucoma and Parkinson’s disease, however, can also cause a thinning of the retina.
Inconsistent test results might also come from differences between the machines most often used for these types of measurements, optical coherence tomography (OCT) devices, and how researchers use them.
In the study, the team shows that the topmost layer of neurons in the retina of a mouse model of Alzheimer’s disease exhibit a change in their structural texture.
Combined with data on the changes in the thickness of this layer, the new measurement could prove to be a more easily accessible biomarker of Alzheimer’s.
The new approach can measure the roughness or texture of the nerve fiber layer of the inner retina.
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.
OCT is the optical analog of ultrasound. It works by sending waves of light into tissues and measuring how long they take to come back.
While it is an extremely useful imaging technique commonly used to make a wide array of diagnoses, it has limitations.
To gather more data, the team added a measurement called angle-resolved low-coherence interferometry (a/LCI), which uses the angles of the scattered light to gather more information about the tissue’s structure.
By combining the two measurements, the researchers can extract both thickness and structural information about each layer of the retina.
The team says the a/LCI measurements complement the thickness measurements to improve the potential utility of more quantitative biomarkers for Alzheimer’s.
The researchers are now working to incorporate this added ability into a low-cost OCT system that Wax is developing through a spinoff company called Lumedica.
The key to the design is a 3-D-printed part that uses symmetry to compensate for mechanical inconsistencies that can arise in traditional OCT devices because of things as small as a subtle shift in temperature.
One author of the study is Adam Wax, a professor of biomedical engineering at Duke.
The study is published in Scientific Reports.
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