Measurement of Ocular Blood Flow and Retinal Oxygen Extraction in Diabetic Patients (DM OPF ROXY)

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.

Study Overview

• Status: Recruiting
• Conditions: Diabetes Mellitus
• Intervention / Treatment: Device: • Laser Speckle Flowgraphy (LSFG); Device: • Optical Coherence Tomography (OCT); Device: • Optical Coherence Tomography Angiography (OCT-A)

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Doreen Schmidl, Prof. Priv. Doz. MD.; PhD; Phone Number: +431404002981; Email: doreen.schmidl@meduniwien.ac.at
• Study Contact Backup: Name: Doreen Schmidl, Prof. Priv. Doz. MD, PhD; Phone Number: +431404002981

Study Locations

• Austria
  • State of Vienna
    • Vienna, State of Vienna, Austria, 1090
      • Recruiting
      • Medical University Vienna

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Diagnostic
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Diabetes mellitus GLP1-RA; Measurements of the Ocular Blood Flow and Retinal Oxygen Extraction are performed.	Device: • Laser Speckle Flowgraphy (LSFG); Laser Speckle Flowgraphy (LSFG); Device: • Optical Coherence Tomography (OCT); • Optical Coherence Tomography (OCT); Device: • Optical Coherence Tomography Angiography (OCT-A); • Optical Coherence Tomography Angiography (OCT-A)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Ocular blood flow (LSFG)	Ocular Blood Flow measured by Laser Speckle Flowgraphy (LSFG) in arbitrary units	From enrollment to last study day (=5-11 weeks)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Retinal vessel diameter	Retinal vessel diameter with DVA	From enrollment to last study day (=5-11 weeks)
Retinal oxygen saturation	Retinal oxygen saturation with DVA	From enrollment to last study day (=5-11 weeks)
Retinal oxygen extraction	Retinal oxygen extraction will be calculated from measurements of ocular blood flow and retinal oxygen saturation. The calculation will be based on a formula integrating these parameters to estimate retinal oxygen extraction. Unit of Measure: Arbitrary units	From enrollment to last study day (=5-11 weeks)
Oxygen and carbon dioxide partial pressure in arterialized blood	Oxygen and carbon dioxide partial pressure in arterialized blood	From enrollment to last study day (=5-11 weeks)
Central retinal thickness	Central retinal thickness with OCT	From enrollment to last study day (=5-11 weeks)
Retinal nerve fiber layer thickness	Retinal nerve fiber layer thickness with OCT	From enrollment to last study day (=5-11 weeks)
Retinal and choroidal microvasculature	Retinal and choroidal microvasculature with OCT-A	From enrollment to last study day (=5-11 weeks)
Capillary blood glucose level	Capillary blood glucose level in mg/dL	From enrollment to last study day (=5-11 weeks)
Autonomic and sensomotoric neuropathy measurements	Short-term spectral analysis of Heart rate variability (HRV) is obtained from recordings consisting of 256 seconds of artifact free recordings. Parameters of frequency-domain HRV are measured within the low-frequency band and high-frequency band, as well as total spectral variability. Outcome variables are spectral power (ms2) in both frequency bands as well as cumulative indices.	From enrollment to last study day (=5-11 weeks)
Ocular perfusion pressure	Ocular perfusion pressure is calculated from systemic blood pressure and intraocular pressure. Unit of measurement: mmHg	From enrollment to last study day (=5-11 weeks)
Intraocular pressure	Intraocular pressure	From enrollment to last study day (=5-11 weeks)
Systemic hemodynamics - Blood pressure	Systolic and diastolic blood pressure is measured. Unit: mmHg	From enrollment to last study day (=5-11 weeks)
Schirmer I Test	Schirmer I Test is performed. Unit of measuremnt: mm	From enrollment to last study day (=5-11 weeks)
Finger sweat sampling	Finger sweat samples will be collected using stamped-out filter paper applied to the fingertip under standardized conditions. Samples will be analyzed using an untargeted multi-omics approach. Proteomic, eicosadomic, and metabolomic profiles will be assessed using high-resolution mass spectrometry platforms. Unit of Measure: Arbitrary units (normalized intensity values)	From enrollment to last study day (=5-11 weeks)
Systemic hemodynamics - Heart rate	Heart rate is measured. Unit: Hz	From enrollment to last study day (=5-11 weeks)
Systemic hemodynamics - Oxygen saturation	Oxygen saturation is measured. Unit: %	From enrollment to last study day (=5-11 weeks)

Collaborators and Investigators

• Sponsor: Medical University of Vienna

Study record dates

Study Major Dates

• Study Start (Actual): November 28, 2025
• Primary Completion (Estimated): May 1, 2026
• Study Completion (Estimated): June 1, 2026

Study Registration Dates

• First Submitted: June 30, 2025
• First Submitted That Met QC Criteria: April 10, 2026
• First Posted (Actual): April 17, 2026

Study Record Updates

• Last Update Posted (Actual): April 17, 2026
• Last Update Submitted That Met QC Criteria: April 10, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Endocrine System Diseases; Metabolic Diseases; Glucose Metabolism Disorders; Nutritional and Metabolic Diseases; Diabetes Mellitus; Investigative Techniques; Diagnostic Techniques and Procedures; Diagnosis; Tomography; Diagnostic Imaging; Tomography, Optical; Optical Imaging; Tomography, Optical Coherence
• Other Study ID Numbers: OPHT-25022025

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No