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

This study has been completed.
Sponsor:
Information provided by:
Medical University of Vienna
ClinicalTrials.gov Identifier:
NCT00812526
First received: December 18, 2008
Last updated: December 19, 2008
Last verified: December 2008
  Purpose

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.


Condition Intervention
Autoregulation
Procedure: Suction cup application
Procedure: Squatting

Study Type: Interventional
Study Design: Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: Open Label
Primary Purpose: Basic Science
Official Title: Regulation of Choroidal Blood Flow During Combined Changes in Intraocular Pressure and Arterial Blood Pressure

Further study details as provided by Medical University of Vienna:

Primary Outcome Measures:
  • Relationship between ocular perfusion pressure and choroidal blood flow [ Time Frame: 4 study days ] [ Designated as safety issue: No ]

Secondary Outcome Measures:
  • Choroidal blood flow [ Time Frame: 4 study days ] [ Designated as safety issue: No ]
  • Mean arterial pressure [ Time Frame: 4 study days ] [ Designated as safety issue: No ]
  • Intraocular pressure [ Time Frame: 4 study days ] [ Designated as safety issue: No ]
  • Systolic/diastolic blood pressure [ Time Frame: 4 study days ] [ Designated as safety issue: Yes ]

Enrollment: 18
Study Start Date: September 2002
Study Completion Date: September 2004
Primary Completion Date: September 2004 (Final data collection date for primary outcome measure)
  Eligibility

Ages Eligible for Study:   19 Years to 35 Years
Genders Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes
Criteria

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
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00812526

Locations
Austria
Department of Clinical Pharmacology, Medical University of Vienna
Vienna, Austria, 1090
Sponsors and Collaborators
Medical University of Vienna
Investigators
Study Director: Elzbieta Polska, MD Department of Clinical Pharmacology, Medical University of Vienna
  More Information

No publications provided

Responsible Party: Gerhard Garhöfer, MD, Department of Clinical Pharmacology, Medical University of Vienna
ClinicalTrials.gov Identifier: NCT00812526     History of Changes
Other Study ID Numbers: OPHT-190702
Study First Received: December 18, 2008
Last Updated: December 19, 2008
Health Authority: Austria: Agency for Health and Food Safety

Keywords provided by Medical University of Vienna:
Choroid
Regional blood flow
Autoregulation
Laser Doppler flowmetry

ClinicalTrials.gov processed this record on October 22, 2014