Clinical trial NCT00712764: Role of Adenosine in the Control of Choroidal Blood Flow During Changes in Ocular Perfusion Pressure.
Official title: Role of Adenosine in the Control of Choroidal Blood Flow During Changes in Ocular Perfusion Pressure.
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Ocular Physiology
Microcirculation
Keywords: Adenosine
Choroidal blood flow
Suction cup
Lead sponsor: Medical University of Vienna
Sponsor class: OTHER
First posted: 2008-07-10
Enrollment: 20
Sex: MALE
Minimum age (years): 18
Maximum age (years): 35
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: TREATMENT

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 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. Adenosine, an endogenous purine metabolic end product with a potent vasodilatory effect on multiple vascular beds, leads to an increase in retinal and choroidal vessel diameter. The present study aims to investigate whether adenosine plays a role in choroidal autoregulation 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 and presence of adenosine.


Eligibility criteria: Inclusion Criteria:

* Men aged between 18 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

Primary outcomes:
measure: choroidal pressure-flow relationship
timeFrame: 2 hours at 2 study days
Secondary outcomes:
Other outcomes:
Locations:
city: Vienna
country: Austria
facility: Department of Clinical Pharmacology, Medical University of Vienna
Study officials:
affiliation: Department of Clinical Pharmacology, Medical University of Vienna
name: Michael Wolzt, MD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Schmidl D, Weigert G, Dorner GT, Resch H, Kolodjaschna J, Wolzt M, Garhofer G, Schmetterer L. Role of adenosine in the control of choroidal blood flow during changes in ocular perfusion pressure. Invest Ophthalmol Vis Sci. 2011 Jul 29;52(8):6035-9. doi: 10.1167/iovs.11-7491.