Measurement of Ocular Blood Flow and Retinal Oxygen Extraction in Diabetic Patients

The prevalence of diabetes is increasing, with type 2 diabetes mellitus comprising over 90% of cases. Diabetes mellitus complications, including diabetic retinopathy (DR), impose significant health burdens. GLP-1 receptor agonists (GLP-1RAs) and dual GIP/GLP-1 receptor agonists show promise in improving cardiovascular and kidney outcomes, but their effects on retinal microvasculature and neuroprotection remain unclear. This study investigates the impact of GLP-1RAs (semaglutide, liraglutide) and GIP/GLP-1-dual agonists (tirzepatide) on ocular blood flow and retinal function in DM patients.

Inclusion Criteria: * Men and women aged ≥ 18 years * Signed informed consent * Previously diagnosed diabetes mellitus * Normal ophthalmic findings except diabetic retinopathy, unless the investigator considers an abnormality to be clinically irrelevant * Planned initiation of therapy with GLP-1 receptor agonist (Semaglutide, Ozempic®; Liraglutide, Victoza®) or GIP/GLP-1 receptor agonist (Tirzepatide, Mounjaro®) by a diabetes specialist Exclusion Criteria: * Participation in a clinical trial in the 3 weeks preceding the screening visit * Symptoms of a clinically relevant illness in the 3 weeks before the first study day * Presence or history of a severe medical condition, except diabetes, as judged by the clinical investigator * Abuse of alcoholic beverages * Blood donation during the previous three weeks * Presence of any abnormalities preventing reliable measurements in the study eye as judged by the investigator * Previous laser photocoagulation treatment in the study eye * Best corrected visual acuity \< 0.4 Snellen * Women of childbearing potential (neither menopausal, nor hysterectomized, nor sterilized) not using effective contraception * Pregnancy, planned pregnancy or lactation