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

Autoregulation Clinical Trial

Official title:

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

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT00812526
• Other study ID #: OPHT-190702
• Status: Completed
• Phase: N/A
• First received: December 18, 2008
• Last updated: December 19, 2008
• Start date: September 2002
• Est. completion date: September 2004

Study information

• Verified date: December 2008
• Source: Medical University of Vienna
• Contact: n/a
• Is FDA regulated: No
• Health authority: Austria: Agency for Health and Food Safety
• Study type: Interventional

Clinical Trial Summary

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.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 18
• Est. completion date: September 2004
• Est. primary completion date: September 2004
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: Male
• Age group: 19 Years to 35 Years

Eligibility

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

Study Design

Allocation: Non-Randomized, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Basic Science

Related Conditions & MeSH terms

• Autoregulation

Intervention

Procedure:
• Suction cup application

• Squatting

Locations

Country	Name	City	State
Austria	Department of Clinical Pharmacology, Medical University of Vienna	Vienna

Sponsors (1)

Lead Sponsor	Collaborator
Medical University of Vienna

Country where clinical trial is conducted

Austria, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Relationship between ocular perfusion pressure and choroidal blood flow		4 study days	No
Secondary	Choroidal blood flow		4 study days	No
Secondary	Mean arterial pressure		4 study days	No
Secondary	Intraocular pressure		4 study days	No
Secondary	Systolic/diastolic blood pressure		4 study days	Yes