MAPT and diabetes mellitus: Considering that sublethal impairment of RGCs synapses could result in progressive dying back toward the cell body, which cannot be reversed once developed, rescue of synaptic loss via knock-down of tau in the retina at a time when RGCs apoptosis not yet occurs appears to have a widespread beneficial effect on the overall health of RGCs, leading to remarkable improvements in visual functions impaired by HFD-induced diabetes.