Ocular Vascular Occlusive Disorders

863 Pages·2015·83.844 MB·English

by  Sohan Singh Hayreh (auth.)

Sohan Singh Hayreh
Ocular Vascular
Occlusive Disorders
123
Ocular Vascular Occlusive Disorders

Sohan Singh Hayreh

Ocular Vascular
Occlusive Disorders
Sohan Singh Hayreh
Department of Ophthalmology
and Visual Sciences
University of Iowa Hospitals and Clinics
Iowa City, IA
USA
ISBN 978-3-319-12780-4 ISBN 978-3-319-12781-1 (eBook)
DOI 10.1007/978-3-319-12781-1
Springer Cham Heidelberg New York Dordrecht London
Library of Congress Control Number: 2015932662
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Dedicated to all my patients
with ocular vascular occlusive disorders

Pref ace
Ocular vascular occlusive disorders – that is, retinal, ciliary and optic nerve
vascular occlusive disorders – collectively constitute the most common cause
of visual loss. However, there have been only a few detailed studies dealing
with just one or the other issue of some of these diseases and their fi ndings
confl ict. There have been no comprehensive, systematic studies dealing with
all aspects of these disorders, laying out the basic scientifi c facts and explain-
ing their pathogeneses. Unfortunately, a good deal of the information has
been based on clinical impressions, folklore, dogma, and “conventional wis-
dom”, taught by one generation of ophthalmologists to the next. That results
in the “bandwagon jumping phenomenon”. Also, as Sir William Osler stated:
“The greater the ignorance the greater the dogmatism”. That has led to much
confusion and controversy on most of the basic and clinical issues in these
disorders.
I have investigated all these disorders systematically since 1955 by doing
basic, experimental and clinical studies. Based on the fi ndings of my scien-
tifi c studies, I have often challenged and contradicted dogmas and the “con-
ventional wisdom” [1]. As Thomas Henry Huxley wrote: “The great tragedy
of Science—the slaying of a beautiful hypothesis by an ugly fact.”[2]. But the
facts are what we need, even if they are sometimes ugly and unwelcome.
When dogmas and “conventional wisdom” are challenged, even when new
scientifi c information shows that they are no longer valid, the initial reaction
is almost always skepticism or even ridicule. I have experienced that so often.
In a small way, I liken myself to Giordano Bruno (1548–1600) who was
burned alive and Galileo Galilei (1564–1642) who was placed under house
arrest for contradicting the “conventional wisdom” – but both were proved to
be right in the end! The objective of this book is to clarify the understanding
of ocular vascular occlusive disorders, in the light of the best current scien-
tifi c knowledge, and to put their management on a rational basis.
D uring my studies of ocular vascular occlusive disorders, I have found that
one major reason for confusion and controversy about these diseases has been
lack of understanding of the basic scientifi c facts. The other major reason has
been the unthinking application of fi ndings from superfi cially similar disor-
ders in other organs to ocular vascular occlusive disorders, even though the
two differ fundamentally in aspects such as morphology, physiology, pathol-
ogy and pathogenesis. As will be evident from the information in the book,
that is often an error, and one that results in confusion and controversy about
the pathogenesis and management of these disorders. Fortunately, knowledge
vii
viii Preface
is constantly evolving and advancing. An in-depth understanding of the
m orphology, blood supply and circulation of the eye and optic nerve, the
factors that infl uence its blood fl ow, and the pathogenesis of various types of
ocular vascular occlusive disorders is crucial if we are to understand and
manage these diseases rationally; after all, the basic sciences are the founda-
tion of Medicine. In this book, I have tried to lay out in detail the basic proven
facts about various aspects of ocular vascular occlusive disorders. Therefore,
the fi rst section of the book covers the relevant basic scientifi c information on
ocular vascular occlusive disorders; the second section deals with the etiol-
ogy, pathogenesis, clinical features and management of the different types of
ocular vascular occlusive disorders.
Some may comment that there is repetition of information among various
chapters. There are many common factors and issues between the various
aspects of different ocular vascular occlusive disorders, so that a certain
amount of repetition among the various chapters is unavoidable, for proper
discussion and understanding; however, to minimize that, I have, where
appropriate, made reference to other chapters which contain detailed infor-
mation on those particular topics, instead of repeating the whole thing.
Finally, since most persons tend to read only the parts which interest them
specifi cally, I have intentionally repeated some information in various chap-
ters in order to make each chapter self-contained and self-explanatory.
S ome clinical ophthalmologists may comment that I have gone to exces-
sive length in some places, in discussing the basic scientifi c facts, pathogen-
eses and controversies. But since these diseases are due to vascular disorders,
an in-depth understanding of the blood supply and blood fl ow of the eye and
other related issues is key to understanding their pathogeneses. Also, when
dealing with a subject such as ocular vascular occlusive disorders, which has
attracted ongoing controversy, one has to give a detailed scientifi c back-
ground. Based on the most current scientifi c facts, I have discussed contro-
versial issues candidly and fully, sometimes discussing issues raised in those
controversies point by point, to place them in proper perspective. Some may
consider that an unorthodox way of dealing with controversies in a book, but
I feel that is the only way the reader can logically understand the context and
the subject. It is my sincere hope that the information in this book helps
toward a wider and better understanding of the various ocular vascular occlu-
sive disorders and the controversies.
I have frequently described or referred to my own studies while discussing
the subject. Since ocular vascular occlusive disorders have been the focus of
my research work since 1955, most of the information in the book is based on
my published studies. A search of Medline and other indices of literature
revealed thousands of articles by others, published on many aspects of ocular
vascular occlusive disorders. Their scientifi c credibility varies enormously.
Reviewing the scientifi c literature can be highly confusing and frustrating.
Langley [3], back in 1899, succinctly stated that “Those who have occasion
to enter into the depths of what is oddly, if generously, called the literature of
a scientifi c subject, alone know the diffi culty of emerging with an unsoured
disposition. …… Much that he is forced to read consists of a record of
defective experiments, confused statements of results, wearisome description
Preface ix
of detail, and unnecessary protracted discussion of unnecessary hypotheses.”
From my experience, I can attest to that. I have tried to cover as many relevant
publications as possible. No doubt, I must have unintentionally missed some
good material for one reason or another, and I apologize for that. I have liber-
ally used material from my own previous publications where appropriate,
when I do not have a better way to present or phrase it than I did in those
publications. In general, I have tried to avoid information from anecdotal case
reports or mere comments, which, in my opinion, do not necessarily provide
valid information. I have also avoided, as far as possible, using comments
from review articles written primarily by reviewers who have not themselves
conducted scientifi c studies on the subject.
O ver the years, I have had invaluable help from many persons while
conducting research in various ocular vascular occlusive disorders, as is
evident from my co-authors in various publications; without their help it would
not have been possible to research all the types of ocular vascular occlusive
disorders in detail, over a period of more than half a century. I am extremely
grateful to them for their help. Since I interpreted the data and wrote the pub-
lished papers myself dealing with various disorders discussed in this book, the
views expressed in those are mine. I take full responsibility for their contents
and I stand behind them. In view of that, unlike many authors, I have chosen
to describe the fi ndings of my research studies in the fi rst person in the book
rather than in the third person and passive voice; however, that does not mean
in any way I take all the credit for the studies. (I am grateful that my publish-
ers, Springer Verlag, do not object to that preference.)
1. Hayreh SS. Prevalent misconceptions about acute retinal vascular
occlusive disorders. Prog Retin Eye Res. 2005;24:493–519.
2 . Huxley TH. Presidential address at the British Association. Biogenesis
and Abiogenesis. Collected Essays. 1870;8:229.
3. Langley JN. Presidential address to the Physiology Section. Report of
the British Association for the Advancement of Science, London 1899. From
Strauss MB, editor. Familiar medical quotations. Boston: Little Brown; 1968.
p. 274.
Iowa City, IA, USA Sohan Singh Hayreh