Dexamethasone Intravitreal Implant for the Treatment of Persistent Diabetic Macular Edema

Inclusion Criteria: * Able to provide written informed consent and comply with study assessments for the full duration of the study. * Age ≥ 18 years * Diagnosis of diabetes mellitus (type 1 or 2) * Any one of the following will be considered to be sufficient evidence that diabetes is present: * Current regular use of insulin for treatment of diabetes * Current regular use of oral anti-hyperglycemia agent for the treatment of diabetes * Clinical evidence of retinal thickening due to macular edema involving the center of the macula associated with diabetic retinopathy. * Previous history of anti-vegf treatment for diabetic macular edema (DME) with documented incomplete resolution of central subfield thickening by spectral-domain optical coherence tomography (SDOCT). At least 4 intravitreal anti-vegf injections within the past six months prior to the baseline study visit are required for eligibility. * Central diabetic macular edema present on clinical examination and SDOCT testing with central 1 mm subfield thickness greater than 300 microns as measured on SDOCT at the baseline visit. * Visual acuity score greater than or equal to 19 letters (20/400) and less than or equal to 74 letters (20/32) by the ETDRS visual acuity protocol. * Media clarity, pupillary dilation and patient cooperation sufficient to allow SDOCT testing and retinal photography. Exclusion Criteria: * Pregnancy (positive pregnancy test) or known to be pregnant; also pre-menopausal women not using adequate contraception. * Participation in another ocular investigation or trial simultaneously * Blood pressure \> 180/110 mmHg (systolic above 180 OR diastolic above 110 mmHg) * Any condition that, in the opinion of the investigator, would preclude participation in the study (e.g. chronic alcoholism, drug abuse) * Evidence of vitreoretinal interface abnormality after ocular exam or OCT that may be contributing to the macular edema * An eye that, in the investigator's opinion, has no chance of improving in visual acuity following resolution of macular edema (e.g. presence of subretinal fibrosis or geographic atrophy) * Presence of another ocular condition that may affect the visual acuity or macular edema during the course of the study (e.g. AMD, uveitis, Irvine-Gass) * Evidence of active neovascularization of the iris or retina * Evidence of central atrophy or fibrosis in the study eye * Presence of substantial cataract, one that might decrease the vision by 3 or more lines of vision at sometime during the study. * History of vitreous surgery in the study eye * History of cataract surgery within 3 months of enrollment. * History of YAG capsulotomy within 2 months of enrollment. * Visual acuity \<20/400 on ETDRS visual acuity charts in the fellow eye * Uncontrolled glaucoma (pressure \> 30 mmHg) despite treatment with glaucoma medications. * History of cerebral vascular accident or myocardial infarction within 3 months prior to Day 0. * Use of systemic steroids (eg, oral, intravenous, intramuscular, epidural, rectal, or extensive dermal) within one month prior to the baseline study visit