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 (HC). We recruited AD and VD patients aged 50–90 years and age-matched HC who underwent ocular optical coherence tomography (OCT) and OCT angiography. Exclusion criteria included cataract, retinopathy, optic neuropathy, intraocular pressure ≥ 21 mmHg, and refractive error greater than + 4.0 D or less than − 4.0 D. 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 HC (p = 0.034 overall ANOVA), while the difference between AD and HC was more pronounced in the inferior zone (p = 0.029). We found significantly thinner RNFL in VD than HC in superior, inferior and temporal quadrants (superior; 121.8 μm vs. 133 μm, p = 0.017, inferior; 126.6 μm vs. 137.3 μm, p = 0.017, temporal; 67.5 μm vs. 73.8 μm, p = 0.043). VD also had overall reduced macular thickness compared to AD, more pronounced in nasal perifoveal area (275.2 μm vs. 285.5 μm, p = 0.039). Overall, VD was characterized by pronounced RNFL and macular thinning, whereas AD exhibited parafoveal vascular density reduction without overt structural thinning.