Evaluation of Bromocriptine, Metoprolol and Tamsulosin in Eyes With Non-Central DME

Inclusion Criteria: * Age \>18 years * Type 1 or type 2 diabetes mellitus * Best corrected visual acuity using the early treatment diabetic retinopathy study (ETDRS) visual acuity test letter score ≥ 74 (i.e., 20/32 or better) within 30 days of enrollment. * On clinical exam, definite retinal thickening due to DME within 3,000 μm of the center of the macula but not involving the 500 μm central subfield. * Thickened non-central macular subfields on the spectral domain OCT macular map * Central subfield thickness within threshold definition for normal central subfield thickness * No focal/grid laser within the last 6 months or other treatment for DME within the last 4 months. * Pseudophakia Exclusion Criteria: * Patients with active proliferative diabetic retinopathy * Pan retinal photocoagulation within the last 12 months of study initiation * A condition that, in the opinion of the investigator, would preclude participation in the study, e.g., unstable medical status including blood pressure, cardiovascular disease, and glycemic control. * Subjects experiencing poor glycemic control who, within the last 4 months, initiated intensive insulin treatment (a pump or multiple daily injections) or plan to do so in the next 4 months. * Use of systemic corticosteroids or anti-VEGF (vascular endothelial growth factor) therapy. * Participation in an investigational trial that involves treatment with any drug within 30 days of randomization that has not received regulatory approval at the time of study entry. Note: study participants cannot receive another investigational drug while participating in this study. * Known allergy or hypersensitivity to any component of the study drugs. * Postpartum women with a history of coronary artery disease or other severe cardiovascular conditions (a bromocriptine contraindication). * Planned glaucoma surgery (floppy iris syndrome associated with tamsulosin therapy). * Blood pressure \> 180/110 mmHg (systolic above 180 or diastolic above 110 mmHg). * If blood pressure is brought below 180/110 by anti-hypertensive treatment, an individual can become eligible. * Subjects with second or third degree heart block (metoprolol contraindication). * Subjects with asthma or other bronchospastic disease (metoprolol precaution). * Individuals currently taking one of the study medications or a medication in the same therapeutic class (beta receptor antagonists, alpha-1 receptor antagonists, or bromocriptine). * Participants expecting to move out of the area of the clinical center to an area not covered by another clinical center during the 12 months of the study. * For women of child-bearing potential: pregnant or lactating or intending to become pregnant within the next 12 months. Women who are potential study participants should be questioned about the potential for pregnancy. Investigator judgment will be used to determine when a pregnancy test is needed.