To evaluate the 3-year visual and morphological outcomes of diabetic macular edema (DME) based on the morphological pattern observed on optical coherence tomography (OCT) after intravitreal ranibizumab injections.

Thirty-two eyes of 32 patients with DME were classified according to the following OCT features: diffuse retinal thickening (DRT), cystoid macular edema (CME), and serous retinal detachment (SRD). All patients received 3 consecutive monthly intravitreal injections of 0.5 mg ranibizumab. After 3 injections, patients received ranibizumab or dexamethasone implantation as needed. The primary outcome was the number of treatments received based on the DME type over 36 months. Best-corrected visual acuity (BCVA), central subfoveal thickness, and macular volume changes were also evaluated.

The eyes were classified as DRT (n = 16), CME (6), or SRD (10). The mean number of injections over 3 years was significantly different among the groups: DRT (4.25), CME (7.5), SRD (7.6; p = 0.048). The number of patients who did not need additional treatment after the initial 3 injections was 13 with DRT (81.3%), 2 with CME (33.3%), and 5 with SRD (50%; p = 0.045). BCVA at 36 months significantly improved from baseline in the DRT group ( p = 0.003). The CME group showed the worst BCVA among the groups ( p = 0.023). Six patients who received intravitreal dexamethasone implantation showed no significant improvement of BCVA but significant decrease in macular volume from 12 to 36 months.

Clinical courses varied according to the morphological pattern of DME after intravitreal ranibizumab injection, and patients with DRT maintained visual and anatomical improvement with fewer injections over 36 months. Additional dexamethasone implantation showed limited effect in reducing macular edema with persistent macular cystic change, but no significant improvement in visual acuity.