Serum levels of placental growth factor reflect the severity of retinopathy of prematurity

Retinopathy of prematurity (ROP) is a neovascular disorder of the immature retina and a leading cause of preventable blindness worldwide.1 A two-phase hypothesis for ROP pathogenesis has been suggested.1 Phase one is vaso-obliteration, where physiological vascularity is compromised and retinal vascular development is delayed by a hyperoxic environment. This induces vasoconstriction, with decreased levels of vascular endothelial growth factor (VEGF) and insulin growth factor-1. Phase two is vasoproliferation, where the avascular retina becomes hypoxic and releases angiogenic factors.