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

Medical University of Vienna

Status

Completed

Conditions

Autoregulation

Treatments

Procedure: Squatting

Procedure: Suction cup application

Study type

Interventional

Funder types

Other

Identifiers

NCT00812526

OPHT-190702

Details and patient eligibility

About

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.

Enrollment

18 patients

Sex

Male

Ages

19 to 35 years old

Volunteers

Accepts Healthy Volunteers

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