Differentiating Alzheimer’s Disease and Vascular Dementia via Combined OCT and OCT‑Angiography Analysis

The purpose of this cross-sectional study is to compare microvascular and structural retinal parameters between Alzheimer's disease (AD), vascular dementia (VD), and healthy controls (HCs). We recruited AD and VD patients aged 50–90 years and age-matched HCs who underwent ocular optical coherence tomography (OCT) and OCT angiography. Exclusion criteria included cataract, retinopathy, optic neuropathy, intraocular pressure ≥21 mmHg, and refractive error ≥±4D. The analysis included 118 participants: 29 with AD (14 female, mean age 70.0 ± 7.5), 30 with VD (11 female, mean age 69.9 ± 9.9) and 59 HC (28 females, mean age 69.7 ± 8.6 years). Parafoveal SCP VAD was slightly lower in AD than VD and HCs (p=0.034 overall ANOVA), while the difference between AD and HCs was more pronounced in the inferior zone (p=0.029). We found significantly thinner RNFL in VD than HCs in superior, inferior and temporal quadrants (superior; 121.8μm vs. 133μm, p=0.017, inferior; 126.6μm vs. 137.3μm, p=0.017, temporal; 67.5μm vs. 73.8μm, p=0.043). VD also had overall reduced macular thickness compared to AD, more pronounced in nasal perifoveal area (275.2μm vs. 285.5μm, p=0.039). Overall, VD was characterized by pronounced RNFL and macular thinning, whereas AD exhibited parafoveal vascular density reduction without overt structural thinning.