ROP pathogenesis and suggested treatments. (a) Retina vessels in the process of their formation and progressive covering of the retina surface. (b) Hyperoxia at this formative stage suppresses VEGF and, consequently, results in regression of newly formed vessels. (c) Upon return to normal air, the ischemic retina upregulates VEGF to high levels, causing excessive formation of leaky vessels. To antagonize VEGF at this stage has been suggested as a strategy to reduce adverse vessel formation. (d) An alternative strategy proposed by Shih et al. (2) is to protect retina vessels from oxygen-induced obliteration through administration of PlGF-1.