Layer-specific choroidal vascular adaptation to high-altitude hypoxia revealed by functional OCT at 3,800 m

This study reveals that the human choroid mounts a depth-specific vascular response to high-altitude hypoxia. Rather than showing uniform vasodilation, superficial choroidal perfusion decreases, whereas deep choroidal perfusion increases and remains elevated after prolonged altitude exposure. The strong relationship between deep choroidal perfusion and arterial blood gases suggests that hypoxia-driven vasodilation outweighs hypocapnic vasoconstriction. These data highlight functional OCT as a powerful tool for measuring how physiological stress reshapes ocular vascular function and suggest that combining high-altitude exposure with depth-resolved functional OCT may provide a useful terrestrial model for vascular changes relevant to spaceflight-associated neuro-ocular syndrome.