Optic Nerve Head Autoregulation During Changes in Arterial Blood Pressure

Study Overview
=================
Brief Summary
-----------------
Constant despite changes in perfusion pressure. It is observed in many vascular beds of the human body to prevent that variations in perfusion pressure are directly transmitted into changes in blood flow. This is necessary to prevent ischemia and/or hypoxia during decreased blood flow and bleeding or increased capillary pressure during increased blood flow. In the eye, several studies have reported that retinal blood flow is autoregulated over a wide range of ocular perfusion pressures. Unfortunately only few data are available for the optic nerve head. To gain data about autoregulation is of special importance given that several important ocular diseases such as glaucoma and age-related macular degeneration are associated with impaired autoregulation. In humans most data were collected using laser Doppler flowmetry. The present study aims to investigate the phenomenon of transient reduction in blood flow and to gain insight in the regulatory mechanisms of optic nerve head blood flow during isometric exercise.

Conditions
-----------------
Decreased Vascular Flow

Intervention / Treatment
-----------------
* Other: Isometric exercise


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Men and women aged between 18 and 35 years, nonsmokers Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant Normal ophthalmic findings, ametropia less than 3 diopters 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 oral contraceptives) Symptoms of a clinically relevant illness in the 3 weeks before the first study day Blood donation during the previous 3 weeks

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Healthy subjects<br> | Other: Isometric exercise<br>* use of a handgrip for 3x2 minutes<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Optic nerve head blood flow |  | 12 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Systolic/diastolic blood pressure |  | 14 minutes | 
| Intraocular pressure |  | at baseline and minute 13 | 
| Pulse rate |  | 14 minutes | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
isometric exercise, Blood flow autoregulation, optic nerve head blood flow, Autoregulation, ocular physiology