Numerous systemic conditions impact ocular health. Eye symptoms may indicate systemic diseases and warrant workups with labs. Conversely, systemic disease may explain or help diagnose ocular disorders.
In the Injury Theory, it's damage to the arterial endothelium, followed by platelet activation, then smooth muscle cell migration to injury, then macrophages, with resulting "foam cells." Engorged foam cells burst, starting the injury cycle all over again