Background and Aim: Diabetic macular edema (DME) is one of the leading causes of visual impairment among working-aged people responsible for more than 10,000 new cases of blindness per year. Although there are some therapeutical options for this disease, most of them are invasive, expensive, subject to a range of side effects, and may not be accessible to the entire population. In addition, conventional eye drops are not able to adequately deliver the drug to the posterior chamber of the eye, where DME develops. In this setting, it has been suggested that topical dexamethasone-cyclodextrin microparticle eye drop (TDCME) formulation may be effective in treating DME. The aim of this manuscript is to describe a study protocol for evaluating the efficacy of this formulation, compared with intravitreal injection of ranibizumab.

Design: Phase II, randomized, double-dummy, multicenter, controlled, non-inferiority clinical trial.

Participants: Adults aged >18 year-old, diagnosed with controlled diabetes (type I or II), and refractory moderate to severe DME in at least one eye at the beginning of study.

Measurements and procedures: Participants will be allocated to either the intervention or control group using block randomization, through a centralized off-site computer interactive response system. The treatment group will receive sham intravitreal injections plus TDCME, whereas the control group will receive intravitreal injection of ranibizumab (0.5 mg) plus EnduraTM (artificial tears eye drops emulsion, used as placebo). While injections will be performed every month, eye drops will be given three times a day (every 8 hours). The primary efficacy outcome will be the change in best corrected visual acuity (BCVA) between baseline and at the end of the 12-month-follow-up time.

Ethical aspects: This trial will be carried out according to the tenants of the Declaration of Helsinki and other international guidelines. Participants will be required to provide informed written consent prior to enrolling in the study. A Data Safety Monitoring Board will be established to follow the study.