Retinal deposits are elevated in Alzheimer’s disease

Researchers examined the potential to noninvasively detect and quantify deposits in the retinas of patients with Alzheimer’s disease by using a solid lipid curcumin fluorochrome and a modified point scanning laser ophthalmoscope.

In the study published in JCI Insight, the mean retinal amyloid index score in 10 patients with Alzheimer’s disease was elevated compared to six healthy controls.

Representative images from the fully automated and blinded image-procession steps involved conversion of raw retinal images and calculation of retinal amyloid index (RAI) scores.

Fluorescent fundus images had a controlled and uniform image-processing analysis to improve signal, reduce noise and identify spots with significantly increased fluorescence.

The integrated intensity values for an Alzheimer’s disease (AD) patient with an RAI score of 55.7 and 65 positive deposits was reported vs. a healthy control with an RAI score of 11.2 and 15 positive deposits.

Neuropathologically confirmed AD patients underwent a histological examination of retinas, which revealed certain layer and geographical distribution of amyloid -protein (A) deposits, especially in previously disregarded retinal regions, according to researchers. Amyloid deposits were found as clusters in the peripheral superior quadrants, often along blood vessels, in AD patients.

Researchers found a significant linear correlation between RAI scores and retinal deposit number, with AD patients showing increased RAI scores and spot numbers vs. healthy controls.

Retinal deposits (spots) were also elevated in AD patients, they said.

“These results expand past identification of retinal A plaques and A peptides in the retinas of AD patients and further demonstrate the existence of classical retinal deposits and morphologies relevant to AD neuropathology, including neuritic-like plaques and NFT-like structures,” researchers wrote.

Additionally, retinal deposits frequently appeared in clusters and, although smaller, mirrored A plaque morphology and vascular pathology in the brain.

They added that retinal plaques were also associated with retinal neuronal loss in these patients.

Furthermore, AD patients showed a substantial increase in A-containing deposits compared with age- and sex-matched healthy controls.

The researchers suggest the utility of noninvasive retinal amyloid plaque imaging as a surrogate biomarker of AD. – by Abigail Sutton

Disclosure: Koronyo is a founding member of NeuroVision Imaging. Please see the full study for all remaining authors’ financial disclosures.