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Contact Lens Use Under Adverse Conditions Applications in Military Aviation Working Group on Contact Lens Use Under Adverse Conditions Committee on Vision Commission on Behavioral and Social Sciences and Education National Research Council National Academy Press Washington, D.C. 1990

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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of dis- tinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Frank Press is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Samuel O. Thier is president of the Institute of Medicine The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Frank Press and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council. Additional copies of this report are available from: Committee on Vision National Research Council 2101 Constitution Avenue N.W. Washington, D.C. 20418 Printed in the United States of America

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WORKING GROUP ON CONTACT LENS USE UNDER ADVERSE CONDITIONS KENNETH POLSE (Chair), School of Optometry, University of California, Berkeley (optometry) JOHN W. CHANDLER, Clinical Science Center, University of Wisconsin (ophthalmology) JAMES P. HUGHES (IOM), Oakland, California (occupational medicine) JAMES JENKINS, Department of Theoretical and Applied Mechanics, Cornell Unnrersibr (engineering) DONALD R. KORB, Boston, Massachusetts (optometry) GEORGE W. MERIT, Marietta, Georgia (optometry) MIGUEL F. REFOJO, The Eye Research Institute, Boston, Massachusetts (engineering) 111

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COMMITTEE ON VISION SUZANNE MCKEE (Chair), Smith-Kettlewell Eye Research Foundation, San Prancisco ROBERT BOYNTON (NAS), Department of Psychology, University of California, San Diego LYNN COOPER, Department of Psychology, Columbia University RUSSELL LEE DEVALOIS (NAS), Department of Psychology, University of California, Berkeley MERTON CLYDE FLOM, College of Optometry, University of Houston DONALD HOOD, Department of Psychology, Columbia University JAMES LACKNER, Ashton Graybiel Spatial Orientation Laboratory, Brandeis University ROBERT SHAPLEY, Department of Psychology, New York University LOUIS SILVERSTEIN, Honeywell, Inc., Phoenix, Ariz. KENT ~ STEVENS, Department of Computer and Information Science, University of Oregon ANDREW B. WATSON, NASA Ames Research Center, Moffett Field, Calif. PAMELA EBERT FI=Al1AU, Study Director JOANNE ALBANES, Research Assistant CAROL METCALF, Administrative Secretary 1V

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Foreword The Committee on Vision is a standing committee of the National Research Council's Commission on Behavioral and Social Sciences and Education. The committee provides analysis and advice on scientific issues and applied problems involving vision. It also attempts to stimulate the further development of visual science and to provide a forum in which basic and applied scientists, engineers, and clinicians can interact. Work- ing groups of the committee study questions that may involve engineering and equipment, physiological and physical optics, neurophysiology, psy- chophysics, perception, environmental effects on vision, and treatment of visual disorders. In order for the committee to perform its role effectively, it draws on experts from a wide range of scientific, engineering, and clinical disciplines. The members of this working group were chosen for their expertise in research related to ocular response to contemporary contact lenses and for their familiarity with the application of those research findings to the use of contact lenses in extreme environments. Although the report addresses the risk factors involved in military use of contact lenses, the findings will also be of particular interest to those involved in the design of contact lenses and those responsible for occupational safety and health matters in the private sector. Suzanne McKee, Chair Committee on Vision v

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Preface In response to a request from the llisenrice Aeromedical Research Panel (TARP)? the Committee on Vision established the Working Group on Contact Lens Use Under Adverse Conditions. The working group was asked to summarize current scientific, clinical, and technological issues in the use of contact lenses and to identify the critical factors to be taken into account by TARP in adopting a formal position on the use of contact lenses by U.S. military personnel. 1b accomplish these goals, the working group convened a symposium to review what is known about the design and use of contemporary contact lenses. Special emphasis was given to the use of lenses in extreme environ- mental conditions. The proceedings of that meeting are being published as a separate report of the Committee on Vision 0;lattau, 1990~. In addition to the specialists who participated in the symposium, a number of people contributed in important ways. Roger Wiley and his staff at the U.S. Army Aeromedical Research Laboratory assisted the working group in arranging for presentations by U.S. military personnel both at the symposium and at meetings of the working group. Science writer Greg Mock played an important role in preparing the working group report, demonstrating remarkable ability to interpret and carefully summarize the vast body of clinical and scientific information gathered by the working group during its activities. Pamela Ebert Flattau, the committee's study director, provided valuable assistance in organizing the symposium and preparing the proceedings report. As always, Carol Metcalf, the committee's administrative secretary, provided efficient and sldllful support. Kenneth Poise, Chair Working Group on Contact Lens Use Under Adverse Conditions vi

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Contents 1 Introduction Contact Lens Development, 3 Contact Lens Use in Military Aviation, 3 Military Ophthalmic Policies, 3 Spectacles Versus Contact Lenses, 5 Current Experience, 6 Contact Lens Use in Civil Aviation, 8 2 Adverse Effects of Contact Lenses Factors Eliciting Adverse Effects, 10 Hypoxia, 11 Low Humidity, 11 I-ens Wear Time, 12 Adverse Effects, 13 Infection, 13 Corneal Edema, 13 Superficial Keratitis, 14 Red Eye, 14 Excess Mucus Production, IS Epithelial Microc~sts, 15 Infiltrates, 15 Endothelial Polymegethism, 16 Corneal Molding, 16 Giant Papillary Conjunctivitis, 16 Corneal Vascularization, 17 Lens Intolerance, 17 Meibomitis, 18 Dryness-Related Effects, 18 vii 1 10

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3 Military Aviation Environments and Contact Lens Use Conditions Adverse to Contact Lens Wear, 20 Reduced Pressure at Altitude, 20 Low Humidity and High Air Flow, 21 High Particulate Count in the Cabin, 22 Noxious Gases, Fumes, and Smoke, 22 Unhygienic Conditions for Lens Care, 23 High Acceleration, 24 Rapid Decompression, 24 Inadequate Lens Care Systems or Regular Follow-up Care, 24 Temperature Extremes, 25 Overmotivation, 25 Conditions Requiring Contact Lens Wear, 25 Specific Military Flight Scenarios, 27 F-A-R Missions, 27 T-T-B Missions, 28 Helicopter Missions, 29 4 Evaluating Risks in the Military Aviation Environment High Risk Factors, 30 Low Humidity and High Air Flow, 3f Extended Wear or Overwear, 31 Unhygienic Conditions for Lens Care, 32 Particulates, 33 Inadequate Follow-Up Care, 33 Moderate Risk Factors, 34 Hypoxia, 34 Noxious Fumes, 34 Overmotivation, 34 Minimal Risk Factors, 35 Bubble Formation From Rapid Decompression, 35 High G-Forces, 35 Temperature Extremes, 35 5 Recommendations Restrictions on Contact Lens Use, 36 Spectacle Use as Backup for Contact Lens Use, 37 Lens Fitting by Qualified Specialists, 38 Regular Follow-Up Care by Qualified Specialists, 38 Optimal Lens 13rpe, 39 Conclusion, 40 References . . . V111 20 30 36 41