INTRODUCTION: We explored associations between measurements of the ocular choroid microvasculature and Alzheimer's disease risk. METHODS: We measured the choroidal vasculature appearing in optical coherence tomography scans of 69 healthy, mid-life individuals in the PREVENT Dementia cohort. The cohort was prospectively split into low, medium, and high-risk groups based on the presence of known risk factors (APOE4 genotype and family history of dementia). We used ordinal logistic regression to test for cross-sectional associations between choroidal measurements and Alzheimer's disease risk. RESULTS: Choroidal vasculature was progressively larger between ordinal risk groups, and significantly associated with risk group prediction. APOE4 carriers had thicker choroids and larger vascularity compared to non-carriers. Similar trends were observed for those with a family history of dementia. DISCUSSIONS: Our results suggest a potential link between the choroidal vasculature and Alzheimer's disease risk. However, these exploratory findings should be replicated in a larger sample.