Compensatory retinal blood flow enhancement in cognitively normal ApoE ε4 carriers

This study aims to compare retinal vascular characteristics between ApoE ε4 carriers and non-carriers in healthy individuals. A total of 84 cognitively healthy subjects-64 non-carriers and 20 carriers of the ApoE ε4 allele-were analyzed using swept-source optical coherence tomography angiography (SS-OCTA). In the retinal vascular layer of OCTA images, parameters such as foveal avascular zone (FAZ) area, vessel perimeter, acircularity index (AI), and vascular density (FD) were quantified. Additionally, blood flow areas in the outer retina and choroidal capillaries, as well as the area without perfusion in the superficial vascular complex (SVC), were measured. Compared to non-carriers, carriers of ApoE ε4 exhibited significant reductions in the FAZ area, as well as increased foveal vessel density in both the deep and superficial vascular complexes. No significant differences were observed in AI, FD, blood perfusion area, or perifoveal blood vessel density between the groups. These findings suggest that reduced FAZ area and increased foveal blood flow density in ApoE ε4 carriers may indicate a compensatory mechanism in retinal blood flow, potentially serving as early indicators of Alzheimer's disease (AD).