Effect of Different Dosages of Intravitreal Bevacizumab (Avastin) in the Treatment of Diabetic Macular Edema: a Randomized Controlled Trial

INTERVENTION: Two groups:1.25mg intravitreal bevacizumab at monthly 3 months versus 2.5mg intravitreal bevacizumab; CONDITION: Diabetic Macular Edema PRIMARY OUTCOME: Best‐corrected visual acuity at 6 month; SECONDARY OUTCOME: 1. Retinal thickness measured by optical coherent tomography (OCT) at each visit;2. Proportion of patients with moderate visual loss at 6 months;3. Proportion of patients with stable or gain in vision at 6 months;4. Intraocular pressure measured by non‐contact tonometry (NCT) at each visit;5. Changes in macular function as measured by multifocal electroretinography (mfERG) at each visit;6. Changes in fluorescein angiography at 6 months;7. Change in levels of aqueous VEGF, PEDF and other growth factors / cytokines during the study period; INCLUSION CRITERIA: INCLUSION CRITERIA: 1. Aged 18 years or older; 2. Clinically significant macular edema (CSME) defined according to the ETDRS:‐ Retinal thickening at or within 500µm of the center of the macula; or ‐ Hard exudates at or within 500µm of the center of the macula associated with adjacent retinal thickening; or ‐ A zone or zones of retinal thickening of one disc area in size and at least part of which is within one disc diameter of the center of fovea; 3. Macular edema of at least 250µm involving the fovea, as documented on optical coherent tomography (OCT); 4. Patients with best‐corrected visual acuity of better than 1.3 ETDRS logMAR units; 5. Patients physically fit to receive intravitreal injection; 6. Informed consent.