Effects of Common Topical Glaucoma Therapy on Optic Nerve Head Blood Flow Autoregulation During Increased Arterial Blood Pressure and Artificially Elevated Intraocular Pressure in Healthy Humans

Condition(s) targeted: Glaucoma

Intervention: Timolol (drug) (Drug); dorzolamide (drug) (Drug); brimonidine (drug) (Drug); Laser Doppler flowmetry (Device); Goldmann applanation tonometer (Device); Suction cup method (Procedure)

Phase: N/A

Status: Withdrawn

Sponsored by: Medical University of Vienna

Official(s) and/or principal investigator(s):
Gabriele Fuchsjaeger-Mayrl, MD, Principal Investigator, Affiliation: Department of Clinical Pharmacology

Background 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 circulation has been shown in animals and humans. The exact mechanism behind this autoregulation is still unknown. The motive for the investigation of optic nerve head (ONH) blood flow autoregulation is to enhance the understanding of pathologic eye conditions associated with ocular vascular disorders. To clarify the regulatory mechanisms of ONH microcirculation is of critical importance to understand the pathophysiology of glaucoma, because there is evidence that glaucoma is associated with optic nerve head ischemia. Several studies indicate that a disturbed autoregulation might contribute to glaucomatous optic neuropathy. Currently, five classes of intraocular pressure (IOP) reducing drugs are available for topical therapy in patients with glaucoma or elevated intraocular pressure. These drugs have also vasoactive properties, which may influence both the resting ocular circulation and the autoregulatory mechanisms of blood flow during changes in ocular perfusion pressure. Study objective To investigate the influence of common topical glaucoma therapy on ONH blood flow regulation during changes in IOP and systemic arterial blood pressure.

Official title: Effects of Common Topical Glaucoma Therapy on Optic Nerve Head Blood Flow Autoregulation During Increased Arterial Blood Pressure and Artificially Elevated Intraocular Pressure in Healthy Humans

Study design: Allocation: Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Investigator), Primary Purpose: Basic Science

Primary outcome: Ocular perfusion pressure - ONH blood flow relationship

Secondary outcome: Composite measure: Blood pressure, heart rate

Minimum age: 19 Years. Maximum age: 35 Years. Gender(s): Both.

Criteria:

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

Department of Clinical Pharmacology, Vienna A-1090, Austria

Starting date: September 2008
Last updated: November 20, 2014