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NCT Number: NCT07536516

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.

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Key information

Conditions

Diabetes Mellitus Endocrine System Diseases Glucose Metabolism Disorders Metabolic Diseases Nutritional and Metabolic Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Medical University Vienna

Vienna, State of Vienna, 1090, Austria

Location status: Recruiting

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

• Laser Speckle Flowgraphy (LSFG)

Device

Laser Speckle Flowgraphy (LSFG)

• Optical Coherence Tomography (OCT)

Device
  • Optical Coherence Tomography (OCT)

• Optical Coherence Tomography Angiography (OCT-A)

Device
  • Optical Coherence Tomography Angiography (OCT-A)

Primary outcomes

  1. Ocular blood flow (LSFG)

    Time frame: From enrollment to last study day (=5-11 weeks)

    Ocular Blood Flow measured by Laser Speckle Flowgraphy (LSFG) in arbitrary units

Secondary outcomes

  1. Retinal vessel diameter

    Time frame: From enrollment to last study day (=5-11 weeks)

    Retinal vessel diameter with DVA

  2. Retinal oxygen saturation

    Time frame: From enrollment to last study day (=5-11 weeks)

    Retinal oxygen saturation with DVA

  3. Retinal oxygen extraction

    Time frame: From enrollment to last study day (=5-11 weeks)

    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

  4. Oxygen and carbon dioxide partial pressure in arterialized blood

    Time frame: From enrollment to last study day (=5-11 weeks)

    Oxygen and carbon dioxide partial pressure in arterialized blood

  5. Central retinal thickness

    Time frame: From enrollment to last study day (=5-11 weeks)

    Central retinal thickness with OCT

  6. Retinal nerve fiber layer thickness

    Time frame: From enrollment to last study day (=5-11 weeks)

    Retinal nerve fiber layer thickness with OCT

  7. Retinal and choroidal microvasculature

    Time frame: From enrollment to last study day (=5-11 weeks)

    Retinal and choroidal microvasculature with OCT-A

  8. Capillary blood glucose level

    Time frame: From enrollment to last study day (=5-11 weeks)

    Capillary blood glucose level in mg/dL

  9. Autonomic and sensomotoric neuropathy measurements

    Time frame: From enrollment to last study day (=5-11 weeks)

    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.

  10. Ocular perfusion pressure

    Time frame: From enrollment to last study day (=5-11 weeks)

    Ocular perfusion pressure is calculated from systemic blood pressure and intraocular pressure.

    Unit of measurement: mmHg

  11. Intraocular pressure

    Time frame: From enrollment to last study day (=5-11 weeks)

    Intraocular pressure

  12. Systemic hemodynamics - Blood pressure

    Time frame: From enrollment to last study day (=5-11 weeks)

    Systolic and diastolic blood pressure is measured.

    Unit: mmHg

  13. Schirmer I Test

    Time frame: From enrollment to last study day (=5-11 weeks)

    Schirmer I Test is performed.

    Unit of measuremnt: mm

  14. Finger sweat sampling

    Time frame: From enrollment to last study day (=5-11 weeks)

    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)

  15. Systemic hemodynamics - Heart rate

    Time frame: From enrollment to last study day (=5-11 weeks)

    Heart rate is measured.

    Unit: Hz

  16. Systemic hemodynamics - Oxygen saturation

    Time frame: From enrollment to last study day (=5-11 weeks)

    Oxygen saturation is measured. Unit: %

Study contacts

Contact information is provided by the study sponsor or research team.

Doreen Schmidl, Prof. Priv. Doz. MD, PhD

CONTACT

+431404002981

Doreen Schmidl, Prof. Priv. Doz. MD.; PhD

CONTACT

[email protected]

+431404002981

Sponsors and collaborators

Lead sponsor

Medical University of Vienna

Other

Registry information

Acronym: DM OPF ROXY

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Apr 17, 2026
Registry last updated
Apr 17, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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