Accounting for around two thirds of all dementia cases in older people, Alzheimer’s disease (AD) places a huge burden not only on patients but also their carers and health systems all over the world. Research into novel treatments is ongoing, but the development of new tools to enable earlier diagnosis is another key focus.
Cerebral microvascular changes are increasingly linked to AD and also mild cognitive impairment (MCI) – a potential early-warning sign of AD, but measurement of such changes in the brain is challenging. Researchers at Duke University in North Carolina, USA, decided to investigate how closely the microvascular changes seen in the brain would be mirrored in the retina. To that end, the group used optical coherence tomography angiography (OCT-A) to image 90 eyes from 52 AD participants, 79 eyes from 41 MCI participants, and 269 eyes from 142 healthy controls (1). The results? The team observed significantly decreased VD and PD (in 3 × 3-mm and 6 × 6-mm scans) using ETDRS subfields in AD participants when compared with MCI and control participants. However, the researchers did not see a significant difference between MCI and healthy controls.
Notably, the study excluded patients with other diseases, such as non-Alzheimer’s dementia, high blood pressure, glaucoma and diabetes, so it is unknown whether the differences seen in OCT-A are unique to AD. Nevertheless, the researchers' objective remains unchanged. “The goal is to one day be able to diagnose Alzheimer’s disease in the very early stages,” says corresponding author Sharon Fekrat, Professor of Ophthalmology at Duke University.
For now, the team will continue collecting longitudinal data, as well as studying larger populations, both of which will be crucial in understanding how the retina’s microvascular changes as the disease progresses. Moreover, Fekrat emphasises that, though OCT-A imaging may not offer the early diagnosis they were looking for, all is not lost: “We may have a non-invasive, inexpensive, and quick way to screen large numbers of people for Alzheimer’s disease and enter these individuals into clinical trials,” she says. And that can only be good news for other teams investigating potential therapies.
References
- SP Yoon et al., “Retinal Microvascular and Neurodegenerative Changes in Alzheimer’s Disease and Mild Cognitive Impairment Compared with Control Participants”, Ophthalmol Retina (2019).
