 The main objective of this study is to assess the short-term effects of combination steroidanti-VEGF therapy on visual acuity and retinal thickness on OCT in comparison with that of continued anti-VEGF therapy alone in eyes with persistent central-involved DME and visual acuity impairment despite previous anti-VEGF treatment. This study will provide important information for the design of a future confirmatory phase III clinical trial on the efficacy of combination steroid and anti-VEGF in eyes with persistent DME and vision impairment following previous anti-VEGF therapy. The primary outcome for efficacy will be the mean change in visual acuity at 24 weeks. 