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

Not Applicable

Terminated

• Conditions: Healthy
• Interventions: Drug: NG-monomethyl-L-arginine (L-NMMA); Drug: Phenylephrine; Drug: Physiological saline solution (as placebo); Device: Laser Doppler Flowmetry; Device: Goldmann applanation tonometer; Device: Suction cup

• Registration Number: NCT00914394
• Lead Sponsor: Medical University of Vienna

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.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2009-06-01
• Study First Submitted QC: 2009-06-04
• Study First Posted: 2009-06-05
• Study Start: 2010-10
• Primary Completion: 2011-07
• Status Verified: 2014-11
• Last Update Submitted: 2014-11-13
• Last Update Posted: 2014-11-14

Recruitment & Eligibility

• Status: TERMINATED
• Sex: All
• Target Recruitment: 12

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Phenylephrine	NG-monomethyl-L-arginine (L-NMMA)	-
Physiological saline solution	Goldmann applanation tonometer	-
NG-monomethyl-L-arginine (L-NMMA)	Phenylephrine	-
NG-monomethyl-L-arginine (L-NMMA)	Suction cup	-
NG-monomethyl-L-arginine (L-NMMA)	NG-monomethyl-L-arginine (L-NMMA)	-
Phenylephrine	Phenylephrine	-
Phenylephrine	Suction cup	-
Physiological saline solution	NG-monomethyl-L-arginine (L-NMMA)	-
Physiological saline solution	Laser Doppler Flowmetry	-
Physiological saline solution	Suction cup	-
NG-monomethyl-L-arginine (L-NMMA)	Physiological saline solution (as placebo)	-
NG-monomethyl-L-arginine (L-NMMA)	Laser Doppler Flowmetry	-
NG-monomethyl-L-arginine (L-NMMA)	Goldmann applanation tonometer	-
Phenylephrine	Goldmann applanation tonometer	-
Physiological saline solution	Physiological saline solution (as placebo)	-
Phenylephrine	Physiological saline solution (as placebo)	-
Phenylephrine	Laser Doppler Flowmetry	-
Physiological saline solution	Phenylephrine	-

Primary Outcome Measures

Name	Time	Method
optic nerve head pressure-flow relationship	1 year

Trial Locations

Locations (1)

Department of Clinical Pharmacology, Medical University of Vienna; 🇦🇹 Vienna, Austria