Importance: A case showing sustained structural and functional responses 2 years after a single treatment with ILUVIEN (0.2 µg/day fluocinolone acetonide, FAc) despite suboptimal responses to ranibizumab. Observations: A 68-year-old female patient with diabetic macular oedema (DME) from type 2 diabetes mellitus was first diagnosed in October 2010 and had a baseline visual acuity (VA) of 46 Early Treatment Diabetic Retinopathy Study (ETDRS) letters in the left eye. Central foveal thickness (CFT) was 712 microns. The patient was treated with 11 intravitreal injections of ranibizumab (5 in combination with a small-interfering RNA agent), and by March 2014, VA and CFT were largely unchanged (55 ETDRS letters and 774 microns). The patient was treated with ILUVIEN as she had a pseudophakic lens and a clearly suboptimal response to the prior therapy with ranibizumab. An implant releasing FAc at a dosage of 0.2 µg/day was administered in March 2014, and the optical coherence tomography indicated that the macula was dry after 7 days (CFT was below 300 microns). This was sustained at 6, 12, and 24 months after the treatment. VA improved by 5 letters within 7 days and by 15 letters within 14 days, and this was maintained after 24 months. Throughout the duration of this study, the intraocular pressure was ≤22 mm Hg, and no glaucoma medication was administered. Conclusions and Relevance: In real-life UK practice, this DME patient showed a suboptimal response to multiple intravitreal injections of ranibizumab. When subsequently treated with a single injection of ILUVIEN, there were large and rapid improvements in VA and CFT that were maintained for the following 2 years.