To prospectively investigate morphologic and functional changes after intravitreal bevacizumab for persistent diffuse and clinically significant diabetic macular edema. In total, 26 eyes in 26 patients were treated with three intravitreal injections of bevacizumab (Avastin™) given at 4-week intervals. Study parameters included: visual acuity (VA), perceived visual improvement, central macular thickness as measured by Spectralis OCT, macular sensitivity and fixation pattern as measured by MP-1 microperimetry, and the incidence of ocular and systemic side-effects. At the time of follow-up, 76.9 % of eyes showed a significant improvement in VA (p = 0.012), 38.4 % showed a one-line improvement on the ETDRS chart compared with VA at day 0, 30.7 % showed a two-line improvement, and 7.6 % showed at least a three-line improvement. The mean central macular thickness was 447 microns at day 0 and 311.1 microns at follow-up (p = 0.003). The mean baseline macular sensitivity, by MP-1 microperimetry, was 8.29 dB; at follow -up, macular sensitivity had improved to 14.26 dB (p = 0.025). These results support further controlled trials on the efficacy of intravitreal bevacizumab in treating diabetic macular edema. Microperimetry and OCT are important tools in managing diabetic patients, providing a detailed study of the macular region, particularly when it is necessary to monitor the morphological and functional outcome after various interventions. A good correlation between retinal sensitivity and perceived visual performance was found.