To determine if there is visual benefit with Ozurdex treatment every three months compared to monthly anti-VEGF alone, in subjects with persistent diabetic macular edema. The investigator hypothesizes more frequent administration of Ozurdex in patients that have persistent diabetic macular edema will result in a more rapid and sustained improvement of visual acuity and/or optical coherence topography (OCT) compared to the use of anti-VEGF alone.