OCULAR BLOOD FLOW IN GLAUCOMA

ISBN 10: 90-6299-222-6

ISBN 13: 978-90-6299-222-5

Distributors:

For the USA and Canada: Pathway Book Service

4 White Brook Road

Gilsum, NH 03448 U.S.A.

email: pbs@pathwaybook.com

For all other countries: Kugler Publications P.O. Box 20538

1001 NM Amsterdam, The Netherlands Telefax (+31.20) 68 45 700

website: www.kuglerpublications.com

© 2009 Kugler Publications, Amsterdam, The Netherlands

All rights reserved. No part of this book may be translated or reproduced in any form by print, photoprint, microfilm, or any other means without prior written permission of the publisher. Kugler Publications is an imprint of SPB Academic Publishing bv, P.O. Box 20538

1001 NM Amsterdam, The Netherlands

Glaucoma Societies/Sections of the following countries and regions have agreed to review the report:

Africa, American, Argentina, Asian-Oceanic, Australia and New Zealand, Austria, Azerbaijan, Belgium, Brazil, Bulgaria, Canadian, Chile, Chinese, Colombia, Costa Rica, Croatia, Czech Republic, Denmark, Egypt, Estonia, Europe, Finland, France, Georgia, Germany, Greece, Hungary, Iceland, India, Indonesia, Iran, Ireland, Israel, Italy, Japan, Kenya, Korea, Latin-American, Latvia, Lesotho, Lithuania, Mexico, Netherlands, Nigeria, Norway, Pakistan, Pan America, Pan Arab, Peru, Philippines, Poland, Portugal, Puerto Rico, Rumania, Russia, Serbia, Singapore, Slovakia, Slovenia, South Africa, South-East Asia, Spain, Sweden, Switzerland, Taiwan, Thailand, Turkey, Ukraine, United Kingdom, Glaucoma Research Society, Optometric Glaucoma Society and International Society for Glaucoma Surgery

The more that you read, the more things you will know.

The more that you learn, the more places you’ll go.

Dr. Seuss, I Can Read With My Eyes Shut!

SHOULD MEASUREMENTS OF OCULAR BLOOD FLOW BE IMPLEMENTED INTO CLINICAL PRACTICE?

N. Gupta, R.N. Weinreb

WHAT DO WE STILL NEED TO KNOW?

A. Harris, F. Medeiros, R. Ehrlich, V. Costa, B. Siesky, I. Januleviciene, C. Burgoyne

PREFACE

This is the sixth World Glaucoma Association Consensus. The relationship between ocular blood flow and glaucoma has been discussed for more than a century, and still it uniformly fuels debates at glaucoma meetings throughout the world. Clearly, the results of this report will have broad and significant impact on glaucoma research and clinical practice. The global faculty, consisting of leading authorities on the scientific and clinical aspects of ocular blood flow, will met in Fort Lauderdale on May 2, 2009 to discuss the reports and refine the consensus statements.

Obtaining consensus on the relationship of blood flow to glaucoma was a daunting task. So much has been studied and written, but how much do we really know? As with the previous WGA consensuses, the Glaucoma Blood Flow consensus is based on the published literature and expert opinion. Although consensus does not replace and is not a surrogate for scientific investigation, it does provide considerable value, especially when the desired evidence is lacking. The goal of this consensus was to establish a foundation for ocular blood flow research of glaucoma and the best practice for its testing in clinical practice. Identification of those areas for which we have little evidence and, therefore, need additional research was a high priority. We hope that this consensus will serve as a benchmark of our understanding, and that it will be revised and improved with the emergence of new evidence.

Makoto Araie

Jonathan Crowston

Neeru Gupta

Alon Harris

Ingrida Januleviciene

Jost Jonas

Felipe Medeiros

Georg Michelson

Lou Pasquale

Robert N. Weinreb

ANATOMY AND PHYSIOLOGY

•The central retinal vein drains all blood from the entire retina and the optic nerve head.

Comment: Upon contact-free ophthalmoscopy, a spontaneous pulsation of the central retinal vein can be detected in ~80 to 90% of normal eyes. Since the central retinal vein passes through the optic nerve and then through the cerebrospinal fluid space before piercing through the optic nerve meninges in the orbit, the blood pressure in the central retinal vein should be at least as high as the cerebrospinal fluid pressure within the optic nerve meninges in the orbit plus a (hypothetical) trans-lamina cribrosa outflow resistance.

•Blood flow to the optic nerve and retina is dominated primarily by myogenic and metabolic regulation. The blood flow to the choroid is believed to be primarily regulated mainly by hormonal and neuronal mechanisms. The extent of autoregulation in the choroid is not known.

Comment: Ocular vascular autoregulation maintains adequate blood flow that provides nutrients and oxygen, as well as adequate tissue turgor, to ocular structures in the face of changing metabolic needs and altered ocular perfusion pressure. Such functions are all designed to allow sharp vision at all times.

Atlas of Ocular Blood Flow

Harris et al 2003

Vasculature of the eye. (From: Harris, A. et al., Atlas of Ocular Blood Flow. 2003. Butterworth Heinemann. Reprinted with permission of the publisher.)