Regulation of Choroidal Blood Flow During Combined Changes in Intraocular Pressure and Arterial Blood Pressure

Study Overview
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Brief Summary
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Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. For a long time it had been assumed that the choroid is a strictly passive vascular bed, which shows no autoregulation. However, recently several groups have identified some autoregulatory capacity of the choroid. Choroidal autoregulation was first shown in a rabbit model where intraocular pressure (IOP) and arterial blood pressure could be varied independently. In these experiments regulation of choroidal blood flow was not only dependent on ocular perfusion pressure, but was also dependent on the value of IOP. This indicates that a myogenic mechanism contributes to choroidal autoregulation, because the regulatory capacity is dependent on the transmural pressure. In the model of myogenic autoregulation arterioles change their vascular tone depending on the pressure inside the vessel and outside the vessel. The present experiments are designed to test whether a myogenic mechanism may also be involved in choroidal autoregulation in humans. For this purpose the investigators perform experiments during which the IOP and the arterial blood pressure is increased. According to the myogenic theory of autoregulation one would expect stronger vasoconstriction at lower IOPs for the same increase in ocular perfusion pressure.

Official Title
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Regulation of Choroidal Blood Flow During Combined Changes in Intraocular Pressure and Arterial Blood Pressure

Conditions
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Autoregulation

Intervention / Treatment
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* Procedure: Suction cup application
* Procedure: Squatting


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Men aged between 19 and 35 years, nonsmokers Body mass index between 15th and 85th percentile Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant Normal ophthalmic findings, ametropia < 1 Dpt. Exclusion Criteria: Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study Treatment in the previous 3 weeks with any drug Symptoms of a clinically relevant illness in the 3 weeks before the first study day Blood donation during the previous 3 weeks Presence of intraocular pathology: ocular hypertension, glaucoma, retinal vasculopathy or other retinal diseases

Ages Eligible for Study
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Minimum Age: 19 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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Male

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: Basic Science
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Intervention/Treatment |
| --- |
|Procedure: Suction cup application|nan|
|Procedure: Squatting|nan|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Relationship between ocular perfusion pressure and choroidal blood flow |  | 4 study days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Choroidal blood flow |  | 4 study days | 
| Mean arterial pressure |  | 4 study days | 
| Intraocular pressure |  | 4 study days | 
| Systolic/diastolic blood pressure |  | 4 study days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Choroid, Regional blood flow, Autoregulation, Laser Doppler flowmetry