A Study to Test Whether BI 1815368 Helps People With an Eye Condition Called Diabetic Macular Edema

Inclusion criteria: * ≥18 years of age * Diagnosis of diabetes mellitus (DM) (type 1 or type 2), Haemoglobin A1C (HbA1c) \<12% treated with stable medication for at least 30 days prior to Day 1; no already-set plans for major changes in DM medication (e.g. start of new medication) at the time of screening and baseline * Centre-involved diabetic macular edema (CI-DME) confirmed on spectral domain optical coherence tomography (SD-OCT) with central subfield foveal thickness (CST) ≥320 µm for male and ≥305 µm for female participants in the study eye at screening * Best corrected visual acuity (BCVA) visual acuity Early Treatment Diabetic Retinopathy Study (ETDRS) letter score in the study eye between 24 and 78 (Snellen equivalent range 20/320 to 20/32) at screening Further inclusion criteria apply. Exclusion criteria: * Macular edema considered to be due to other causes than CI-DME in the study eye * Proliferative diabetic retinopathy or iris neovascularisation (including the anterior chamber angle) in the study eye * Any intravitreal (IVT) anti-vascular endothelial growth factor (VEGF) treatment within 4 months before Day 1 (other than Vabysmo® or Eylea® HD), and within 6 months before Day 1 for Vabysmo® or Eylea® HD, and/or more than 4 prior IVT injections with anti-VEGF treatment in total in the study eye * Any history of panretinal photocoagulation treatment, macular laser photocoagulation, vitreoretinal surgery, IVT or periocular corticosteroid treatment (within 12 months before Day 1), history of Iluvien® or Ozurdex® implants before Day 1, or topical steroid or NSAID treatment (within 30 days before Day 1) * Active ocular inflammation of any history of intraocular inflammation within 1 year * Aphakia or total absence of the posterior capsule; Yttrium aluminium garnet (YAG) laser capsulotomy in the study eye is permitted if more than 2 months prior to Day 1 Further exclusion criteria apply.