Healthy
Conditions
Keywords
flicker induced changes, total volumetric retinal blood flow
Brief summary
Neurovascular coupling or functional hyperemia is defined as an essential physiologic mechanism in the brain, which is necessary for the local adaption of blood flow to altered metabolic demands of the tissue. It has been shown that also in the eye, blood flow is considerably coupled to retinal neural activity. The current concept of functional hyperemia is that visual stimulation, as flicker light, effectuates increasing neural activity in the retina, which elevates the metabolic needs of the retinal tissue for oxygen and glucose and consequently induces dilatation and augmented blood flow in the retinal vasculature. In several studies, stimulation with flicker light has been shown to induce an increase of blood flow in major retinal arteries and veins as well as an increase of optic nerve head blood flow. Up until now, flicker induced changes in blood flow were measured solely in the major retinal arteries and veins with systems such as the commercially available dynamic vessel analyzer (DVA) by Imedos and with laser Doppler velocimetry (LDV). In the present study, the investigators propose to measure the response of total retinal blood flow to diffuse luminance flicker stimulation with bi-directional Fourier Domain Doppler Optical Coherence Tomography (FDOCT) as well as with Laser Speckle Flowgraphy (LSFG) in healthy subjects by assessing vessel diameter, blood velocity and blood flow of all retinal vessels. For comparative reasons, the investigators will furthermore assess the blood flow of major retinal arteries and veins with the dynamic vessel analyzer (DVA) and laser Doppler velocimetry (LDV).
Interventions
Sponsors
Medical University of Vienna
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* Informed consent for participation * Men and women aged between 18 and 45 years * Non-smokers * Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant * Systolic blood pressure \< 140 mmHg, diastolic blood pressure \< 90 mmHg * Normal ophthalmic findings, ametropia less than 3 diopters
Exclusion criteria
* History or presence of ocular disease * Ametropy ≥ 3 dpt * Treatment with any drug in the 3 weeks preceding the first study day * Symptoms of a clinically relevant illness in the 3 weeks before the first study day * Participation in a clinical trial in the 3 weeks preceding the first study day * Blood donation during the 3 weeks preceding the first study day * History of family history of epilepsy * Abuse of alcoholic beverages * Pregnancy
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Flicker induced changes in total retinal blood flow (FDOCT) | 1 day |
Secondary
| Measure | Time frame |
|---|---|
| Red blood cell velocity (LDV) | 1 day |
| Retinal vessel diameters (DVA) | 1 day |
| Retinal oxygen saturation (DVA) | 1 day |
| Relative Flow Volume (LSFG) | 1 day |
Countries
Austria
Outcome results
None listed