Pfeiffer et al. measured and found that insulin-like growth factor I (IGF-I), IGF-II, IGF binding protein 2 (IGFBP-2), and IGFBP-3 were elevated 3–13 fold in nondiabetic retinal ischemia and 1.5–3 fold in PDR [55]. Here, IGF1 is linked to retinal ischemia.