Although clinical information on the relationship between glycemic control and retinal neurodegeneration and macular microvasculature is not available, the major components of the renin-angiotensin system have been identified to be overexpressed in the retina of DM patients, and the blockade of the system in experimental models of DM attenuated retinal neurodegeneration [31,32]. The gene discussed is REN; the disease is diabetes mellitus.