A Study to Evaluate the Safety, Tolerability, Pharmacodynamics, and Pharmacokinetics of RO7823653 in Participants With Diabetic Macular Edema (DME)

Inclusion Criteria: * Diagnosis of diabetes mellitus (type 1 or type 2), as defined by the World Health Organization (WHO) and/or American Diabetes Association * Glycated hemoglobin (HbA1c) \<= 12% * For study eye: Macular thickening secondary to DME involving the center of the fovea with central subfield thickness (CST) \>= 325 micrometers (µm) as measured by SD-OCT and BCVA of 65 to 35 letters Exclusion Criteria: * Currently untreated diabetes mellitus or previously untreated participants who initiated oral anti-diabetic medication or insulin within 90 days prior to Day 1 * Pregnant or breastfeeding, or intending to become pregnant during the study or within the timeframe in which contraception is required * Uncontrolled blood pressure * For Parts 1 and 2: Any history of ocular injection/implant therapy (e.g., anti-vascular endothelial growth factor agents (anti-VEGF), anti-VEGF/anti-angiopoietin-2 (Ang-2 agents), corticosteroids, device implant. * For Part 3: History of treatment with any of the following: Aflibercept 2 mg, ranibizumab, bevacizumab, or anti-VEGF biosimilars within 90 days prior to Day 1; Aflibercept 8 mg, brolucizumab, or faricimab within 120 days prior to Day 1; Triamcinolone acetonide (IVT, suprachoroidal, or periocular) within 120 days prior to Day 1; Dexamethasone intravitreal implant within 180 days prior to Day 1; Fluocinolone acetonide (FA) intravitreal implant within 3 years prior to Day 1; Device implant * History of uveitis, vitritis (grade trace or above), and/or scleritis in either eye * Active intraocular inflammation in either eye * Any previously documented or current proliferative diabetic retinopathy (PDR) in the study eye