Background: to report the anatomical and functional outcome based on patterns of optical coherence tomography (OCT) morphology in diabetic macular edema (DME), following treatment with intravitreal ranibizumab (IVR) injection. Aim of the Work: to evaluate the role of OCT in detecting the patterns of DME and its effect on anatomical and functional outcome after IVR injection. Patients and Methods: this study enrolled 30 eyes of patients with DME. These patients were categorized into 3 groups according to OCT finding, group I- 10 eyes with diffuse retinal thickening (DRT), group II- 10 eyes with cystoid macular edema (CME), group III- 01 eyes with neurosensory detachment (NSD). All patients received a three monthly doses of intravitreal ranibizumab. Best-corrected visual acuity (BCVA) and central macular thickness (CMT) were assessed before and after the treatment (in the 1st, 3rd and 6th month). Results: at month 6, mean BCVA changed with 0.24 ± 0.057 Decimal (P<0.001),0.23± 0.10 Decimal (P<0.001) and 0.11 ± 0.12 Decimal (P=0.019), respectively, for DRT, CME and NSD groups. Mean CMT decreased by119.80 ± 84.58μm (P=0.002) in DRT group, by83.00 ± 65.98μm (P=0.003) in CME group and by 102.30 ± 110.25 μm (P=0.017) in NSD group. The DRT group was associated with superior BCVA improvement and greater reduction in CMT. Conclusion: we found statistically significant improvement of BCVA and CMT in all groups of DME based on OCT pattern at final follow-up with greater reduction in CMT and superior BCVA improvement in DRT group.