This study is open to adults with diabetic retinopathy. People who have non-proliferative diabetic retinopathy of moderate or high severity can join the study. The purpose of this study is to find out whether a medicine called BI 764524 helps people with diabetic retinopathy. The study also aims to find a suitable treatment plan for BI 764524. Participants are put into 5 groups by chance. Participants in groups 1, 2, and 3 get BI 764524. Over 1 year, they get a different number of injections of the same dose of BI 764524 injected into 1 eye. During some visits, participants may get a sham control, which is done like an eye injection but without a needle, so that participants will not know how many injections of BI 764524 they received. Participants in group 4 only get a sham control. Participants in group 5 (only in the USA) get aflibercept or sham injections during some visits. Aflibercept is a medicine already used to treat diabetic retinopathy. Participants are in the study for one and a half years. During this time, they visit the study site at least 16 times. During this time, doctors regularly do eye exams and visual tests to assess the severity of participants' eye condition. After 1 year of treatment, researchers look at the number of participants with eye improvements. To do so, they compare eye damage and certain severe eye problems between the groups of participants. The doctors also regularly check participants' health and take note of any unwanted effects.