The purpose of the investigator's study is to evaluate the efficacy and safety profile of the pro re nata (PRN) regimen to 12 months by using intravitreal dexamethasone implant in eyes with treatment-naive diabetic macular edema patients.

Pathogenesis of diabetic macular edema (DME) involves inflammation, angiogenesis, and oxidative stress processes provoked mainly by cytokines such as interleukin (IL)-6, 8, and monocyte chemotactic protein, and vascular endothelial growth factor (VEGF). Vision loss associated with diabetic retinopathy is most commonly caused by DME, which affects approximately 7% of all diabetic patients. Several therapeutic options are available for treating DME. Evidence for the use of these therapies is accumulating; however, the optical treatment choice remains unclear. In recent years, using intravitreal anti-VEGF agents to treat DME has been shown to be beneficial. Anti-VEGF injections are generally considered suitable first-line therapy for center-involved DME and are effective in improving visual acuity (VA), with 10% to 40% of patients achieving significant improvement in best-corrected visual acuity (BCVA) after 1 year of treatment.

The management of DME is complex, and often multiple treatment approaches are needed. Although anti-VEGF agents were effective for the treatment of DME, there is a proportion of patients who do not achieve optimal response to these agents, presenting refractory or persistent DME. Intravitreal administration of steroids for the treatment of DME has also been studied for many years due to their well-known, widespread, anti-inflammatory effects. Dexamethasone implant is a slow-release dexamethasone delivery system developed for intravitreal administration that has recently been introduced as a therapeutic option in DME.

Inclusion Criteria:

1. Male and females 18 years of age or older
2. Written informed consent has been obtained
3. Diabetic macular edema with a central macular thickness (CMT) ≥ 300um measured by spectral domain optical coherence tomography.
4. Treatment-naïve subjects for diabetic macular edema.
5. Documented BCVA of ETDRS letter score of 23 to 73 letters (Snellen equivalent of 20/320 to 20/40) in the study eye.

Exclusion Criteria:

1. Previous panretinal photocoagulation (PRP) or macular laser photocoagulation in the study eye
2. Any prior or concomitant ocular treatment (e.g. anti-VEGF therapy, corticosteroids) in the study eye for diabetic macular edema
3. Prior systemic anti-VEGF or corticosteroid therapy, investigational or approved, within the last 3 months before the first dose in the study
4. Previous use of intraocular corticosteroids in the study eye at any time or use of periocular corticosteroids in the study eye within 12 months prior to Day 1
5. Elevated intraocular pressure or a history of steroid-induced ocular hypertension
6. The presence of other retinopathies, maculopathies, visually significant cataract, vitreomacular traction, peripheral ischemia, history of pars plana vitrectomy
7. Any active intraocular, extraocular, and periocular inflammation or infection in either eye within 4 weeks of screening
8. Any history of allergy to povidone iodine