Assessment of individual retinal layer thickness and vascular changes in Alzheimer's disease

Alzheimer's disease (AD) is a leading cause of dementia, underscoring the need for early and accurate diagnostic methods. This cross-sectional study examines the thickness of individual retinal layers and vessel density (VD) in 23 patients with AD and 22 healthy controls (HC). All participants underwent comprehensive ophthalmologic assessments and cognitive evaluations. AD patients exhibited significantly reduced mean macular retinal thickness compared to HC in foveal and parafoveal areas (p < 0.05). The most significant differences were noted in specific sectors of the Inner Nuclear Layer (INL) and Outer Nuclear Layer (ONL) (p < 0.05), while no significant changes were found in the Outer Retinal Layer (p > 0.05). Additionally, AD patients showed decreased VD in the deep vascular plexus (DVP) (p = 0.030) and an increased foveal avascular zone (FAZ) (p = 0.021). The areas under the receiver operating characteristic curves (AUC) analysis revealed the highest diagnostic accuracy for ONL thickness in the S2 sector (0.79) and for mean macular thickness in C0 and T1 sectors (0.76). Positive correlations were observed in some areas between individual retinal layers and VD in their corresponding vascular plexuses in the AD group. The findings suggest that alterations in retinal layer thickness and VD may serve as potential non-invasive diagnostic markers for AD.