Regulation of Optic Nerve Head Blood Flow During Combined Changes in Intraocular Pressure and Arterial Blood Pressure

Regulation of Optic Nerve Head Blood Flow During Combined Changes in Intraocular Pressure and Arterial Blood Pressure.

Status

Withdrawn

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT00915226

Enrollment

Registered

2009-06-05

Start date

2009-09-30

Completion date

2010-10-31

Last updated

2014-11-14

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Healthy

Keywords

Optic disk, Regional blood flow, Autoregulation

Brief summary

Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. The existence of an effective autoregulation in the optic nerve head (ONH) circulation has been shown in animals and humans. Moderate elevation of intraocular pressure (IOP) caused only slight effect on ONH blood flow in monkeys, cats and rabbits. In humans, during an artificial IOP rise using a suction cup method the ONH blood flow maintains almost constant until IOP reaches 40-55 mmHg. During isometric exercise the upper limit of autoregulation appears to be approximately 40% above the baseline ocular perfusion pressure. The mechanism behind ONH blood flow autoregulation is still unknown. The present experiments are designed to improve the investigators' knowledge of the physiology of regulatory mechanisms in ONH circulation, which may be helpful for a better understanding of blood flow abnormalities in glaucoma. This is of importance, because there is an increased evidence, that vascular dysregulation plays a role in the development of glaucomatous damage.

Interventions

PROCEDURESuction cup application

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

PROCEDURESquatting

Squatting

Study design

Allocation

NON_RANDOMIZED

Intervention model

CROSSOVER

Primary purpose

BASIC_SCIENCE

Masking

NONE

Eligibility

Sex/Gender

MALE

Age

19 Years to 35 Years

Healthy volunteers

Yes

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 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

Design outcomes

Primary

Measure	Time frame
Ocular perfusion pressure - ONH blood flow relationship	9 months

Countries

Austria

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 4, 2026