WGA Consensus Series 6: Ocular Blood Flow in Glaucoma

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, have 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

See also: International Glaucoma Review
World Glaucoma Association

For the World Glaucoma Association Consensus VI, our topic was Blood Flow in Glaucoma. Global experts were assembled beginning in November 2008 to participate in the Project Forum E-Room, a unique aspect to facilitate discussion of each of the consensus meetings.

With each of the prior meetings, arriving at the consensus was circuitous and filled with compromises, and this meeting had a similar path. Nevertheless, this was an excellent opportunity to critically assess the evidence relating to the relationship between glaucoma and ocular blood flow and develop consensus statements. The meeting, as with previous ones, was stimulating, educational, thought-provoking, and enjoyable for all participants and attendees.

Robert N. Weinreb
Alon Harris

Preface
Welcome

ANATOMY AND PHYSIOLOGY
L. Pasquale, J. Jonas, D. Anderson

Anatomy of blood from the heart to the eye
Blood supply of the optic nerve
Overview of blood flow regulation in general
The mediators of autoregulation
The anatomic underpinning of ocular blood flow control
The ocular vasculature and its role in regulating blood flow to the optic nerve and retina

CLINICAL MEASUREMENT OF OCULAR BLOOD FLOW
A. Harris, I. Januleviciene, B. Siesky, L. Schmetterer, L. Kageman, I. Stalmans, A. Hafez, M. Araie, C. Hudson, J. Flanagan, S.T. Venkataraman, E.D. Gilmore, G. Feke, D. Huang, E. Stefánsson

Color Doppler Imaging
Laser Doppler Flowmetry and Scanning Laser Flowmetry
Retinal Vessel Analyzer
Blue Field Entopic Stimulation
Laser Interferometric Measurement of Fundus Pulsation
Dynamic Contour Tonometry and Ocular Pulse Amplitude
Pulsatile Ocular Blood Flow (POBF) Analyzer
Laser Speckle Method (Laser Speckle Flowgraphy)
Digital Scanning Laser Ophthalmoscope Angiography
Bi-directional Laser Doppler Velocimetry and Simultaneous Vessel Densitometry
Doppler Optical Coherence Tomography
Retinal Oximetry

CLINICAL RELEVANCE OF OCULAR BLOOD FLOW (OBF) MEASUREMENTS INCLUDING EFFECTS OF GENERAL MEDICATIONS OR SPECIFIC GLAUCOMA TREATMENT
M. Araie, J. Crowston, A. Iwase, A. Tomidokoro, C. Leung, O. Zeitz, A. Vingris, L. Schmetterer, R. Ritch, M. Kook, A. Harris, R. Ehrlich, D. Gherghel, S. Graham

What is the evidence supporting a role for ocular blood flow in glaucoma patients?
Clinical evidence derived from different measurement parameters
Evidence from experimental animal studies
What disease mechanisms lead to impaired blood flow in glaucoma?
Ocular versus systemic causes
Systemic factors
Vascular dysregulation/perfusion instability
What is the impact of medication and other modifiable factors on ocular blood flow?
IOP-lowering topical medication
Systemic drugs
Ocular surgery, exercise
Does modulation of blood flow alter glaucoma progression?
Glaucoma and systemic vascular disease
Systemic disease and glaucoma patients
Diabetes
Cardiovascular diseases

SHOULD MEASUREMENTS OF OCULAR BLOOD FLOW BE IMPLEMENTED INTO CLINICAL PRACTICE?
N. Gupta, R.N. Weinreb

Interpreting clinical studies

WHAT DO WE STILL NEED TO KNOW?
A. Harris, F. Medeiros, R. Ehrlich, V. Costa, B. Siesky, I. Januleviciene, C. Burgoyne

Ocular blood flow and visual function in glaucoma patients
Ocular perfusion pressure and prevalence and progression of glaucoma
Ocular blood flow and optic nerve head structure
The relationship between intraocular pressure and ocular blood flow
The relationship between cerebrospinal fluid pressure and glaucoma
Future research

Summary of Consensus Points
Index of authors