In this randomized clinical trial, 100 eyes with nonproliferative diabetic retinopathy will be included and divided randomly into 2 groups: Intravitreal Bevacizumab group (50 eyes) that receive 6 bimonthly intravitreal bevacizumab, and control group (50 eyes) that undergo regular follow-up for Diabetic Retinopathy. Diabetic macular edema (DME) will be treated independently in all groups by intravitreal bevacizumab. Primary outcome will be the percentage of patients with progression of 2 or more stages through international diabetic retinopathy staging. The secondary measures will be changes in best corrected visual acuity (BCVA) and central macular thickness (CMT), and number of examinations and injection.

Inclusion Criteria:

• Presence of severe NPDR with DRSS score more than 53 with or without diabetic macular edema
• Diagnosis of DM (type 1 or 2) with age more than 18 years' old
• Visual acuity from 20/25 to 20/40 according to Snellen chart examination or more than 69 letters according to ETDRS chart

Exclusion Criteria:

• Presence of proliferative diabetic retinopathy features including vitreous hemorrhage or optic disc or retinal neovascularization
• History of retinal laser photocoagulation
• Tractional retinal detachment involving the macula
• Evidence of neovascularization of angle on examination
• Macular edema due to a cause other than DME
• Any ocular condition which may change visual acuity during the study
• History of intravitreal injection of anti-vascular endothelial growth factor agent in past 3 months
• History of any use of intravitreal corticosteroid
• History of major intra-ocular surgery except cataract surgery in the past 6 months
• History of thromboembolic every in the past 3 months