This results in the release of WBCs and their attachment to the blood vessel wall, in return causing micro-thrombosis in the thin wall of retinal blood vessels and blocking them.14 Another theory is that inflammatory mediators and growth factors such as interleukin-1β can significantly increase the activity of hypoxia-inducing factor (HIF-1α pathway), which induces and intensifies ROP.17 This evidence concerns the gene HIF1A and retinopathy of prematurity.