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Completed

NCT Number: NCT00810927

Role of Nitrogen Oxide (NO) in the Control of Choroidal Blood Flow During a Decrease in Ocular Perfusion Pressure

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 human choroid. In the brain and the retina the mechanism behind autoregulation is most likely linked to changes in transmural pressure. In this model arterioles change their vascular tone depending on the pressure inside the vessel and outside the vessel. In the choroid, several observations argue against a direct involvement of arterioles. However, the mechanism behind choroidal autoregulation remains unclear.

In the present study autoregulation of the choroid will be investigated during a decrease in ocular perfusion pressure, which will be achieved by an increase in intraocular pressure. Pressure/flow relationships will be investigated in the absence or presence of a NO synthase inhibitor. As a control substance the alpha-receptor agonist phenylephrine will be used.

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Key information

Conditions

Physiology, Ocular Autoregulation Microcirculation Regional Blood Flow

Age range

19 year–35 year

Sex eligibility

Male

Study type

Interventional

Phase

Phase 2

Primary location

Department of Clinical Pharmacology, Medical University of Vienna

Vienna, 1090, Austria

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Men aged between 19 and 35 years, nonsmokers
  • Body mass index between 15th and 85th percentile (Must et al. 1991)
  • Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant
  • Normal laboratory values unless the investigator considers an abnormality to be clinically irrelevant
  • Normal ophthalmic findings, ametropia < 3 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
  • History of hypersensitivity to the trial drug or to drugs with a similar chemical structure
  • History or presence of gastrointestinal, liver or kidney disease, or other conditions known to interfere with, distribution, metabolism or excretion of study drugs
  • Blood donation during the previous 3 weeks

Treatment and study plan

Suction cup application

Procedure

he IOP will be raised by a 11 mm diameter, standardized suction cup placed on the temporal sclera with the anterior edge at least 1 mm from the limbus.

Laser Doppler Flowmetry

Procedure

Measurement of choroidal blood flow

Measurement of intraocular pressure

Procedure

Primary outcomes

  1. ocular perfusion pressure - choroidal blood flow relationship

Sponsors and collaborators

Lead sponsor

Medical University of Vienna

Other

Registry information

Official study title

Role of NO in the Control of Choroidal Blood Flow During a Decrease in Ocular Perfusion Pressure

Important dates

Study start
2003
Primary completion
2004
Study completion
2005
First posted
Dec 18, 2008
Registry last updated
Dec 18, 2008

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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