Baget–Bernaldiz M, et al. – This article was composed with the objective to ascertain the changes in the multifocal electroretinogram (mfERG) at 1 year in a clinical series of diabetic macular edema (DME) patients treated with ranibizumab (RNBZ) utilizing a pro re nata protocol. The multifocal electroretinogram allowed us to differentiate groups of eyes with DME as per their electrophysiological profile, both initially and after being treated with RNBZ. Ranibizumab increased the response density in all DME types included in the study, with a maximum response in those eyes with spongiform type. Once treated with RNBZ, the macular electrophysiological activity improved in eyes that had a well–preserved ellipsoid zone and external limiting membrane (ELM). The presence of hard exudates was a limitation to the response density achieved at the foveola.