The aim of this study was to evaluate the electrophysiological changes in diffuse diabetic macular oedema using pattern visual evoked potential before and after laser treatment using modified grid laser treatment. Cases were followed up over 6 months follow up period by clinical examination, pattern visual evoked potential and flouresecin angiogram. The types of laser used for the different groups were the classic argon laser, the mild argon laser or the subthreshold micropulse diode laser treatment. The study highlight the effect of the different types of laser on the electrophysiological function of the macular, and also the effectiveness of these types of laser on the resolution of diabetic macular oedema.