Diabetic macular edema (DME) is a complicated disease due to a multifactorial process comprising the breakdown of the blood retinal barrier with a subsequent fluid accumulation in the macula. Treatment of DME depends recently on more successful therapies such as anti-vascular endothelial growth factor (VEGF) therapies that could stabilize or improve vision in several cases. Ranibizumab has been submitted for approval as a treatment of visual impairment owing to DME.Objective: To assess the response of intravitreal injection (IVI) of ranibizumab in DME at Mansoura ophthalmology center. Patients and methods:This were a prospective study carried out on a total of 50 diabetic cases with DME. Full history was taken from included cases and full ophthalmological examination was conducted in addition to evaluation of the macular retinal maps using optical coherence tomography (OCT) (Spectral domain OCT 2000). Three monthly consecutive intravitreal injections of anti-VEGF of ranibizumab at a dosage of 0.5mg/0.05 ml were administered to all the cases.Results: There was highly statistically significant improvement in the visual acuity (VA) and highly statistically significant reduction in the macular thickness in the included cases after one month and after three months as compared with the pretreatment value (P<0.001). The degree of diabetic control didn't appear to affect the change of the macular thickness. Conclusion:The intravitreal ranibizumab injection effectively decreased macular thickness and improved VA. The structural and functional effects of ranibizumab appeared as early as after 1 month of treatment and maintained at 3 months following treatment.