A research team, led by the Keck School of Medicine of USC, has found that a non-invasive eye exam could potentially serve as a screening tool for diagnosing cerebral small vessel disease in Black Americans and other individuals from underdiagnosed and high-risk populations.
"Most people with cerebral small vessel disease are not diagnosed until significant brain damage has occurred. Damage to the brain cells is not reversible." said Xuejuan Jiang, PhD, associate professor of ophthalmology at the Keck School of Medicine and lead author of the study that was published in the journal Alzheimer's & Dementia: The Journal of the Alzheimer's Association. "This exam might help identify those people who are at high risk of developing cerebral small vessel disease early, while they can still get help."
Using a novel device designed to examine the blood vessels within the retina, the team successfully established connections between specific characteristics in the eye's vasculature and the initial indicators of cognitive decline. These indicators corresponded to structural alterations typically observed in the brains of individuals with cerebral small vessel disease.
Recruited from the African American Eye Disease Study, a population-based study encompassing over 6,000 African Americans in Inglewood, California, the research participants, all aged 40 or above with no history of cognitive impairment, underwent optical coherence tomography angiography (OCTA) at the USC Roski Eye Institute.
OCTA, an emerging imaging technique increasingly integrated into ophthalmology clinical practice, provides detailed images of retinal capillaries without requiring dye injection. Leveraging these images, the team calculated retinal capillary density, blood flow rates, and velocity. Notably, OCTA can detect retinal capillary changes even before clinical symptoms manifest.
Additionally, participants underwent cognitive function assessments, and some received brain magnetic resonance imaging (MRI). The latter enabled the team to measure early structural changes in the brain, recognized as biomarkers for cerebral small vessel disease.
After analyzing the data gathered during the examinations, the team established a link between reduced blood flow rates in retinal capillaries and decreased blood vessel density to functional and structural alterations in the brain associated with cerebral small vessel disease.
Among participants who underwent cognitive assessments, diminished blood flow rates and lower blood vessel density were correlated with impaired information processing speed and executive function. These findings also exhibited associations with three specific MRI measurements known to be indicative of cerebral small vessel disease.
"This indicates that altered retinal blood flow may be a biomarker of early changes in cognition resulting from cerebral small vessel disease," said Jiang, noting that of the two associated measures, the rate of blood flow in the retinal capillaries was a more sensitive measure of changes in the brain. Jiang noted that this technology might also be used to monitor the progression of disease or the efficacy of treatments for cerebral small vessel disease.
Jiang emphasized the significance of the study's inclusion of Black participants. Historically, Black individuals have been underrepresented in research and clinical trials related to dementia and Alzheimer's disease, despite dementia being more prevalent among Black Americans than their white counterparts in the United States.
Furthermore, Jiang highlighted the importance of diversity in studies on cerebral small vessel disease and vascular dementia. These conditions are more prevalent among populations with high rates of diabetes, hypertension, and other vascular diseases, including Black and Latino communities.
“We know how important it is for research to include more diverse patients. There needs to be more research on Blacks and Latinos because they are at higher risk, and we are hopeful that this research is moving in the direction of finding a screening and monitoring tool,” said Xuejuan Jiang, PhD, associate professor of ophthalmology, Keck School of Medicine.
Abdolahi, F. (2023). Retinal perfusion is linked to cognition and brain MRI biomarkers in Black Americans. Alzheimer's & Dementia. doi.org/10.1002/alz.13469