Correlation of Flicker Induced and Flow Mediated Vasodilatation in Patients With Endothelial Dysfunction and Healthy Volunteers.

Study Overview
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Brief Summary
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A couple of studies have shown that illuminating the eye with diffuse flickering light is accompanied by an increase of retinal vessel diameters, optic nerve head blood flow and retinal blood flow. We have recently used this visual stimulation technique as a new and powerful tool for the non-invasive investigation of vascular reactivity. Additionally, we could show that this response is diminished in patients with vascular pathologies and that the response is dependent on nitric oxide, indicating that flicker induced vasodilatation may reflect endothelial dysfunction and may be a new approach to test endothelial function in vivo. One of the most widely used method for the assessment of endothelial function is flow mediated dilatation (FMD). FMD has been shown to give a reliable estimate of vascular function in vivo. In the present study, we set out to compare the standard method for the evaluation of endothelial function, FMD, to flicker induced vasodilatation in the retina.

Official Title
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Correlation of Flicker Induced and Flow Mediated Vasodilatation in Patients With Endothelial Dysfunction and Healthy Volunteers

Conditions
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Diabetes Mellitus, Type 1, Hypertension, Hypercholesterolemia, Regional Blood Flow

Intervention / Treatment
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* Procedure: Forearm blood flow measurement, Flow mediated dilation (FMD)
* Device: Zeiss Retinal Vessel Analyzer (RVA), Stimulation with Flicker-light


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients with diabetic retinopathy: Men and women aged > 18 years. Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant. Inclusion criteria of patients are insulin dependent diabetes mellitus (IDDM) with non or mild non-proliferative diabetic retinopathy. Patients with no signs of diabetic retinopathy (level 1) or patients with one or more microaneurysms (level 2) will be included. Level of diabetic retinopathy will be assessed according to the criteria defined in the AREDS-study.(1991) serum cholesterol < 250 mg/dl (treated or untreated) Patients with mild hypertension and/or hypercholesterinemia: Men and women aged > 18 years. mild essential hypertension defined as a blood pressure meeting the criterion of hypertension grade 1 of the World Health Organisation blood pressure classification systolic blood pressure between 140 and 159 mmHg and diastolic blood pressure between 90 and 99 mmHg and/or serum cholesterol > 250 mg/dl blood pressure will be measured at two different occasion in a sitting positions Healthy subjects: Men and women aged > 18 years. Normal findings in the medical history unless the investigator considers an abnormality to be clinically irrelevant normal ocular findings serum cholesterol < 200 mg/dl systolic blood pressure between 110mmHg and 140mmHg diastolic blood pressure < 90 mmHg Exclusion Criteria: Abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study Symptoms of a clinically relevant illness in the 3 weeks before the first study day Blood donation during the previous 3 weeks other ocular pathologies than diabetic retinopathy level 1 or 2 History or family history of epilepsy Ametropy greater or equal than 3 dpt systolic blood pressure < 100mmHg diastolic blood pressure < 75mmHg pregnant or lactating women

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: 1<br>IDDM | Procedure: Forearm blood flow measurement, Flow mediated dilation (FMD)<br>* Forearm blood flow measurement: baseline 1 min, 3 min after inflation of cuff, 4 min after 0.8mg Nitroglycerin<br>Device: Zeiss Retinal Vessel Analyzer (RVA), Stimulation with Flicker-light<br>* Stimulation with Flicker-light: 1 min, measurement without flickering light 4 min after 0.8 mg Nitroglycerin<br>|
| Other: 2<br>Hypercholesterolemia and/or Hypertension | Procedure: Forearm blood flow measurement, Flow mediated dilation (FMD)<br>* Forearm blood flow measurement: baseline 1 min, 3 min after inflation of cuff, 4 min after 0.8mg Nitroglycerin<br>Device: Zeiss Retinal Vessel Analyzer (RVA), Stimulation with Flicker-light<br>* Stimulation with Flicker-light: 1 min, measurement without flickering light 4 min after 0.8 mg Nitroglycerin<br>|
| Other: 3<br>age/sex matched healthy control subjects | Procedure: Forearm blood flow measurement, Flow mediated dilation (FMD)<br>* Forearm blood flow measurement: baseline 1 min, 3 min after inflation of cuff, 4 min after 0.8mg Nitroglycerin<br>Device: Zeiss Retinal Vessel Analyzer (RVA), Stimulation with Flicker-light<br>* Stimulation with Flicker-light: 1 min, measurement without flickering light 4 min after 0.8 mg Nitroglycerin<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Retinal vessel diameters (Retinal vessel analyzer) |  | 8 min | 
| Forearm Blood Flow |  | 8 min | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Flicker induced vasodilatation, Flow mediated vasodilatation, Forearm blood flow, Retinal vessel diameter, Endothelial dysfunction