Role of Nitric Oxide in Optic Nerve Head Blood Flow Regulation During Experimental Increase of Intraocular Pressure in Healthy Humans

Status

Terminated

Phases

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT00914394

Enrollment

Registered

2009-06-05

Start date

2010-10-31

Completion date

Unknown

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

L-NG-Monomethyl Arginine, Optic Nerve Head Blood Flow, Intraocular Pressure, Regional Blood Flow, Ocular Physiology, Optic Disk

Brief summary

Autoregulation is defined as the ability of a vascular bed to adapt its vascular resistance to changes in perfusion pressure. In the eye, several studies have reported that retinal blood flow is autoregulated over a wide range of ocular perfusion pressures. Large scale studies have shown that reduced ocular perfusion pressure is an important risk factor for the prevalence, the incidence and the progression of primary open angle glaucoma. Former studies that investigated ocular blood flow autoregulation focused mainly on choroidal blood flow. For the optic nerve head only few data are available, although it seems likely that it underlies similar autoregulatory mechanisms. A previous study investigating choroidal blood flow has shown that nitric oxide (NO) plays a key role in choroidal autoregulation. The present study is designed to test the hypothesis that NO plays a role in optic nerve head autoregulation during increased intraocular pressure (IOP). Therefore, IOP will be experimentally increased using a suction cup device in the absence of presence of either a nitric oxide synthase inhibitor (L-NMMA), an α-receptor agonist (phenylephrine) or placebo. Optic nerve head blood flow will be continuously measured during the procedure.

Interventions

DRUGNG-monomethyl-L-arginine (L-NMMA)

bolus 6mg/kg over 5 minutes followed by a continuous infusion of 60µg/kg/min over 15 minutes

DRUGPhenylephrine

1µg/kg/min, infusion period 20 minutes

DRUGPhysiological saline solution (as placebo)

infusion period 20 minutes

DEVICELaser Doppler Flowmetry

Measurements will be performed at the neuroretinal rim to assess ONH blood flow.

DEVICEGoldmann applanation tonometer

intraocular pressure measurements

DEVICESuction cup

Experimental stepwise increase of intraocular pressure while measurement of optic nerve head blood flow.

Study design

Allocation

RANDOMIZED

Intervention model

CROSSOVER

Primary purpose

BASIC_SCIENCE

Masking

TRIPLE (Subject, Investigator, Outcomes Assessor)

Eligibility

Sex/Gender

ALL

Age

18 Years to 35 Years

Healthy volunteers

Yes

Inclusion criteria

* Men and women aged between 18 and 35 years, nonsmokers * Men and women will be included in equal parts * Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant * Normal findings in the laboratory testings unless the investigator considers an abnormality to be clinically irrelevant * Normal ophthalmic findings, ametropia less than 1 diopter

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 (except intake of oral contraceptives) * Symptoms of a clinically relevant illness in the 3 weeks before the first study day * 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 * Pregnancy

Design outcomes

Primary

Measure	Time frame
optic nerve head pressure-flow relationship	1 year

Countries

Austria

Outcome results

None listed

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