Reduced Retinal Perfusion With Preserved Microvascular Network Density in Early Alzheimer's Disease: A Multimodal...

Area of Science:

• Ophthalmology
• Neurology
• Biomedical Engineering

Background:

• Alzheimer's disease (AD) and mild cognitive impairment (MCI) are associated with neurovascular alterations.
• Characterizing these changes in the retina may provide insights into early disease detection and progression.

Purpose of the Study:

• To investigate retinal neurovascular alterations in AD and MCI.
• To examine the relationships between retinal structure and function in these conditions.

Main Methods:

• Eighty-two participants (AD, MCI, and controls) underwent retinal imaging.
• Retinal blood flow (RBF) was measured using a function imager.
• Optical coherence tomography (OCT) angiography and ultra-high-resolution OCT quantified vessel density, perfusion, and tissue volume.

Main Results:

• The AD + MCI group exhibited significantly lower RBF, retinal capillary flow index (RCF), and retinal tissue perfusion (RTP) compared to controls.
• Morphometric indices including retinal vessel density (RVD), retinal vessel length density (RVLD), and capillary perfusion density (CPD) did not differ between groups.
• In AD + MCI, RBF was not associated with microvascular structural metrics, unlike in controls.

Conclusions:

• AD and MCI are characterized by reduced retinal perfusion and capillary flow, despite preserved microvascular network density and retinal tissue volume.
• These findings suggest altered hemodynamic-morphometric relationships in the retina of individuals with AD and MCI.
• Hemodynamic retinal imaging can detect early perfusion impairment, serving as a potential noninvasive biomarker for AD and MCI detection and monitoring.