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 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 faricimab or aflibercept 8mg), and within 6 months before Day 1 for faricimab or aflibercept 8 mg, and/or more than 4 prior IVT injections with anti-VEGF treatment in total in the study eye * Any history of panretinal photocoagulation, macular laser photocoagulation, vitreoretinal surgery, IVT or periocular corticosteroid treatment (within 12 months before Day 1), history of fluocinolone ophthalmic implant or dexamethasone IVT implant 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.