NGF and diabetes mellitus: A similar preventive strategy that treats all patients with NGF eye drops for their entire life, starting from the onset of diabetes, even if successful in preventing DR, would not be feasible in a clinical setting for a number of reasons: (1) only a subset of diabetic patients develops DR and, in particular, its proliferative stage [16]; (2) the long-term side effects of NGF treatment are still unknown, so only patients at risk of DR should be treated; and (3) the cost of treating all diabetic patients with topical NGF would be extremely high.