IGF1 and retinopathy of prematurity: TGFβ-1, VEGF, IGF-1, and HTRA-1 are unique in that they have all been postulated to play a role in ROP and preeclampsia and have a direct and indirect role in angiogenesis (Ajayi et al., 2008; Ferrari et al., 2009; Bergmann et al., 2010; Powers et al., 2010; Marzioni et al., 2012; Chen et al., 2014; Dong et al., 2015; Hentges et al., 2015a; Teoh et al., 2015; Liao et al., 2017; Liu et al., 2018).