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

NCT00812526 | Completed

• 1 other identifier: OPHT-190702
• Study Type: interventional
• Target: 18
• Locations: 1 country
• Sites: 1

Brief 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.

Conditions

Autoregulation

Keywords

Choroid; Regional blood flow; Autoregulation; Laser Doppler flowmetry

Outcome Measures

Primary Outcomes (1)

• Relationship between ocular perfusion pressure and choroidal blood flow

  4 study days

Secondary Outcomes (4)

• Choroidal blood flow

  4 study days

• Mean arterial pressure

  4 study days

• Intraocular pressure

  4 study days

• Systolic/diastolic blood pressure

  4 study days

Interventions

Suction cup application PROCEDURE

Squatting PROCEDURE

Eligibility Criteria

• Age: 19 Years - 35 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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.

You may not qualify if:

• 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

Sponsors & Collaborators

• Medical University of Vienna: lead

Study Sites (1)

Department of Clinical Pharmacology, Medical University of Vienna

Vienna, 1090, Austria

Location

Study Officials

• Elzbieta Polska, MD

  Department of Clinical Pharmacology, Medical University of Vienna

  STUDY DIRECTOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: BASIC SCIENCE
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER

Study Record Dates

• First Submitted: December 18, 2008
• First Posted: December 22, 2008
• Study Start: September 1, 2002
• Primary Completion: September 1, 2004
• Study Completion: September 1, 2004
• Last Updated: December 22, 2008

Record last verified: 2008-12

Locations

AU (1)