Retinal and Choroidal Vascular Changes Associated with Vitamin D Deficiency.

Vitamin D is involved in endothelial regulation, inflammatory control, oxidative stress responses, angiogenesis, and neurovascular homeostasis, providing a biological basis for its potential involvement in the retinal and choroidal circulation. This narrative review synthesizes evidence from studies investigating associations between serum 25-hydroxyvitamin D [25(OH)D] concentrations and ocular vascular parameters assessed using optical coherence tomography (OCT), OCT angiography (OCTA), and retinal vascular imaging. Evidence from adult and pediatric populations generally associated vitamin D deficiency (VDD) with lower vessel density in the superficial and deep capillary plexuses, altered retinal vascular caliber and foveal avascular zone morphology, and reduced choroidal thickness or vascularity. However, the direction and magnitude of retinal OCTA findings were inconsistent, and conventional retinal structural measurements frequently remained unchanged. Supplementation studies reported relatively consistent increases in choroidal thickness and vascularity, whereas retinal perfusion responses were limited. Preliminary studies suggested that correction of VDD might support a more sustained response to bevacizumab in diabetic macular edema and central retinal vein occlusion, although this effect was not demonstrated consistently across retinal vascular diseases. Lower 25(OH)D concentrations were also more frequent among patients with retinal vascular occlusions, but residual systemic vascular confounding limits causal interpretation. Overall, current evidence supports a biologically plausible association between vitamin D status and ocular microvascular health but does not establish causality, functional visual benefit, or a specific therapeutic indication for supplementation. Longitudinal multicenter studies and randomized trials using standardized imaging protocols, functional outcomes, biochemical confirmation of vitamin D correction, and validated automated image analysis are required to determine the clinical relevance and reversibility of these findings.