ROP, a biphasic disease, is initiated with blunted retinal vascular growth in the setting of hyperoxia (phase I), followed by abnormal retinal neovascularization in response to hypoxia-induced intraocular growth factors such as vascular endothelial growth factor (VEGF) (phase II) (Smith et al., 2013). The gene discussed is VEGFA; the disease is retinopathy of prematurity.