NGF and diabetic retinopathy: To verify whether the early development of an OCT-detectable thinning of the RNFL/GCL could be implemented at the same time as a biomarker of diabetic retinopathy and as an effective pharmacological target, we tested the possibility of preventing (secondary prevention) the development of DR by starting neuroprotective treatment (topical NGF) as soon as the thinning of the RNFL/GCL becomes statistically significant.