VEGFA and retinopathy of prematurity: Even though pathological neovascularization in ROP may be prevented with treatment limiting tissue ischemia (laser ablation of the retina) and/or hypersecretion of VEGF (intravitreal injection of anti-VEGF), still a clear understanding of the mechanisms implicated in the progression of ROP from phase 1 to phase 2 is needed to develop new therapeutic alternatives.