How to go to your page This eBook contains four volumes. Each volume has its own page numbering scheme, consisting of a volume number and a page number, separated by a colon. For example, to go to page 5 of Volume 1, type 1:5 in the "page #" box at the top of the screen and click "Go." To go to page 5 of Volume 2, type 2:5… and so forth. The Eyes i THE FACTS ON FILE ENCYCLOPEDIA OF HEALTH AND MEDICINE IN FOUR VOLUMES: VOLUME 1 ii The Eyes Medical Advisory Review Panel Kyra J. Becker, M.D. James C. Blair, III, PA-C Alexa Fleckenstein, M.D. Nancy A. Lewis, Pharm.D. Gary R. McClain, Ph.D. Maureen Ann Mooney, M.D. Margaret J. Neff, M.D., M.Sc. Maureen Pelletier, M.D., C.C.N., F.A.C.O.G. Otelio S. Randall, M.D., F.A.C.C. Susan D. Reed, M.D., M.P.H. Jerry Richard Shields, M.D. Christina M. Surawicz, M.D. Denise L. Wych, R.N., C.M. Editorial Staff James Chambers, General Editor Lee Ann Chearney, Book Producer Deborah S. Romaine, Senior Writer Candace B. Levy, Ph.D., ELS, Copyeditor Cathy Jewell, Proofreader Wendy Frost, Medical Illustrator The Eyes iii THE FACTS ON FILE ENCYCLOPEDIA OF HEALTH AND MEDICINE IN FOUR VOLUMES: VOLUME 1 An Amaranth Book iv The Eyes To your health! The information presented in The Facts On File Encyclopedia of Health and Medicineis provided for research purposes only and is not intended to replace consultation with or diagnosis and treatment by medical doctors or other qualified experts. Readers who may be experiencing a condition or disease described herein should seek medical attention and not rely on the information found here as medical advice. The Facts On File Encyclopedia of Health and Medicine in Four Volumes: Volume 1 Copyright © 2007 by Amaranth Illuminare All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information contact: Facts On File, Inc. An imprint of Infobase Publishing 132 West 31st Street New York NY 10001 Produced by Amaranth Illuminare PO Box 573 Port Townsend WA 98368 Library of Congress Cataloging-in-Publication Data The Facts on File encyclopedia of health and medicine / Amaranth Illuminare and Deborah S. Romaine. p. ; cm. “An Amaranth book.” Includes index. ISBN 0-8160-6063-0 (hc : alk. paper) 1. Medicine—Encyclopedias. 2. Health—Encyclopedias. [DNLM: 1. Medicine—Encyclopedias—English. 2. Physiological Processes—Encyclopedias—English. WB 13 R842f 2006] I. Title: Encyclopedia of health and medicine. II. Romaine, Deborah S., 1956- III. Facts on File, Inc. IV. Title. 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The Eyes v CONTENTS VOLUME 1 Foreword by Maureen Pelletier, M.D., C.C.N., F.A.C.O.G. vii How to Use The Facts On File Encyclopedia of Health and Medicine ix Preface to Volume 1 xiii The Ear, Nose, Mouth, and Throat 1 The Eyes 65 The Integumentary System 125 The Nervous System 212 The Musculoskeletal System 290 Pain and Pain Management 361 Medical Advisory Review Panel 391 Index 395 v vi The Eyes FOREWORD A big part of my role as a physician is educating your body in isolation from other body structures my patients about their health. I take as much and functions. Your body attempts to compensate time as each person needs to explain prevention and adjust, often without your awareness, until it measures, test results, and treatment options. I can no longer accommodate the injury or illness. encourage questions. But in the moment, sitting The symptoms you bring to your doctor may there in my office, most people do not yet know reflect this compensation, for example frequent what to ask me. By the time questions flood headaches that point not to brain tumor (as many their thoughts, they may be back at work or at people fear but is very rare) but to eye strain or home. muscle tension or sometimes to hypertension Numerous events and circumstances can chal- (high blood pressure). lenge health, and we all need to know what In my medical practice I emphasize integrative actions we can take to keep ourselves healthy as health care, embracing the philosophy that health well as to obtain appropriate treatment for health exists as the intricate intertwining of the body’s conditions that do affect us. Knowledge empow- many systems, structures, and functions. So, too, ers all of us to make informed and appropriate does the care of health. I received my medical decisions about health care. Certainly there is no degree from Tufts University School of Medicine shortage of reference material. Yet there is so in Boston, an institution noted for remaining at much information available today! Even for the forefront of the medical profession. I also physicians, it is challenging to keep up. How can completed clinical programs in Mind-Body Medi- you get to the core of what you want to know, cine at Harvard University, Integrative Medicine at reliably and to the level of detail you need? the University of Arizona School of Medicine, and The Facts On File Encyclopedia of Health and Medi- Medical Acupuncture at the University of Califor- cineis a great resource for up-to-date health infor- nia-Los Angeles (UCLA). I am a board-certified mation presented in a manner that is both obstetrician-gynecologist, a board-certified clinical comprehensive and easy to understand no matter nutritionist, and a licensed acupuncturist. I see what your level of medical knowledge. The ency- patients in my practice in Cincinnati, Ohio; I clopedia organizes entries by body system. The teach, I lecture, and I frequently go on television progression of body systems—and entries— and radio to talk about health topics. In each of throughout the encyclopedia presents topics the these areas, I encourage people to think about way you think about them. their health and health concerns from an integra- Going beyond this basic structure, however, is tive perspective. When you understand your another layer of organization that particularly health from multiple dimensions, you can better appeals to me, which is a comprehensive structure understand what to do to keep yourself as healthy of cross references that integrates entries across as possible. body systems. After all, your body functions in an I wish you the best of health for all of a long, integrated way; so, too, should a reference series satisfying life. But when the time comes that you that discusses your body’s health. Not very much must make decisions about medical care, I want that happens with your health affects one part of you to have the knowledge to make informed vii viii Foreword choices that are right for you. Whether you start Encyclopedia of Health and Medicine to be a most here and move on to more specialized resources valuable reference resource. or locate all the information you need within —Maureen M. Pelletier, M.D., C.C.N., these four volumes, you will find The Facts On File F.A.C.O.G.