A Study of the Safety and Efficacy of a New Treatment for Diabetic Macular Edema

350 µg or 700 µg dexamethasone posterior segment drug delivery system - injection into the vitreous cavity not less than every 6 months for up to 36 months.

Sham posterior segment drug delivery system-needle-less drug delivery system without study medication not less than every 6 months for up to 36 months.