Measuring eye blood flow and retinal oxygen use in people with diabetes

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

We will test whether starting GLP‑1 or dual GIP/GLP‑1 drugs (semaglutide, liraglutide, tirzepatide) changes eye blood flow and retinal oxygen use in adults with diabetes.

Quick facts

• Phase: NA
• Study type: Interventional
• Enrollment: 20 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: Medical University of Vienna (other)
• Locations: 1 site (Vienna, State of Vienna)
• Trial ID: NCT07536516 on ClinicalTrials.gov

What this trial studies

This interventional study will use noninvasive imaging—laser speckle flowgraphy (LSFG), optical coherence tomography (OCT), and OCT angiography (OCT‑A)—to measure ocular blood flow and retinal oxygen extraction in people with diabetes before and after initiation of a GLP‑1 receptor agonist or a dual GIP/GLP‑1 agonist. Eligible participants are adults with diagnosed diabetes who plan to start semaglutide, liraglutide, or tirzepatide and who have no major ocular abnormalities that would prevent reliable imaging. Key exclusions include prior laser photocoagulation in the study eye and recent participation in other trials or clinically relevant illness. All imaging and visits take place at the Medical University of Vienna.

Who should consider this trial

Good fit: Ideal candidates are adults with diabetes who are about to begin semaglutide, liraglutide, or tirzepatide and who have no major eye conditions that would interfere with imaging.

Not a fit: Patients with advanced retinal disease, a history of laser photocoagulation in the study eye, or any condition that prevents reliable OCT/OCT‑A/LSFG measurements are unlikely to benefit from participation.

Why it matters

Potential benefit: If positive, the findings could show whether these diabetes drugs improve retinal blood flow or oxygen use and help guide therapy choices to better protect vision.

How similar studies have performed: GLP‑1 receptor agonists and tirzepatide have established cardiovascular and renal benefits, and some preclinical and small human studies hint at retinal or neuroprotective effects, but robust clinical data on retinal blood flow are limited.

Eligibility criteria

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

Where this trial is running

Vienna, State of Vienna

• Medical University Vienna — Vienna, State of Vienna, Austria (RECRUITING)

Study contacts

• Study coordinator: Doreen Schmidl, Prof. Priv. Doz. MD.; PhD

Conditions: Diabetes Mellitus