Phase I/II study with intravitreal triamcinolone acetonide microspheres(RETAAC)for treatment of diffuse diabetic macular edema unresponsive to laser photocoagulation. Study hypothesis is that single intravitreal injection of RETAAC is safe and efficient compared to conventional treatment. Fifty patients will participate in this study and will be randomized into treatment and observation groups. Efficacy will be evaluated by best corrected visual acuity and macular thickness measured by optic coherence tomography (OCT) after 12 months of treatment.

Inclusion Criteria:

• Diabetes mellitus (type 1 or 2)
• Diabetic macular edema in study eye associated to diabetic retinopathy
• Diffuse macular edema defined as macular thickening determined by biomicroscopy and fluorescein angiography.
• Best corrected visual acuity between 34 (20/200) and 68 letters (20/50).
• Macular thickness greater than 300 mcm on OCT.

Exclusion Criteria:

• Uncontrolled systemic disease
• Start of medical therapy for diabetes or change in treatment from oral to insulin four months before initial visit.
• HbA1c levels greater than 10%
• Presence of retinal venous occlusion, cystoid macular edema,or other condition that would contribute to macular edema.
• Presence of epiretinal membrane
• Presence of vitreomacular traction in the study eye.
• Aphakic or anterior chamber intraocular lens in the study eye.
• Neovascularization of disc or elsewhere in the study eye.
• History or presence of choroidal neovascularization in the study eye.
• Presence of rubeosis irides in the study eye.
• Eye opacity that interfere with clinical documentation and photography.
• Intra-ocular surgery 90 days before initial visit.
• Previous vitrectomy in study eye.
• Previous history of intravitreal or periocular corticoid or any other intravitreal drug in study eye.
• Scheduled surgery for study eye.
• Patients with known allergies to fluorescein, iodo-povidone or any component of study drug.