BDNF and glaucoma: Besides NMDA receptor overactivation, other mechanisms of ganglion cell apoptosis of axonal origin such as the loss of retrograde transport of brain-derived neurotrophic factor (BDNF) from optic nerve projection sites in the brain could also contribute to the pathogenesis of glaucoma [29] and the NMDA receptor blockade alone may not be adequate enough for overall RGC protection.