Diabetic retinopathy is a major sight-threatening disease and is a leading cause of blindness. There is an emerging body of evidence that suggests that neuronal changes are an early phenomenon in the diabetic retina and that several cell types are affected, including the ganglion cells. The degeneration of these cells is thought to occur via overstimulation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor. Characteristic features of the normal mammalian retina and of the diabetic retina, and the involvement of NMDA receptors in diabetic retinopathy, are discussed. (c) 2002 Prous Science. All rights reserved.