AK Jain

CBS Publishers & Distributors Pvt LtdDedicated to Education

AK Jain

CBS Publishers & Distributors Pvt Ltd

9 789386 478634

ISBN: 978-93-86478-63-4

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4819/XI, Prahlad Street, 24 Ansari Road, Daryaganj, New Delhi 110 002, India delhi@cbspd.com, cbspubs@airtelmail.in; www.cbspd.com

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Textbook of Optics andRefractive Anomalies

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AK Jain DNB, MNAMS

is currently Assistant Professor, Department of Ophthalmology, Rama Medical College, Hapur. He completed his MBBS from the prestigious Karnataka Institute of Medical Sciences (formerly Karnataka Medical College), Hubli, Karnataka, and postgraduation from a renowned institute, ICARE Eye Hospital and Postgraduate Institute, Noida, UP. He has remained in the academic field since the beginning of his career and actively participated in state and national level ophthalmic conferences where he presented several scientific papers and conducted scientific instruction courses on various ophthalmic conditions.

presents a comprehensive description of and in relation to human eye and refractive errors in human eye.

Informative illustrations explaining the text in relation to the optics and various refractive anomalies are the skeleton of this book.Accurate and precise information about the topic make this book unique in the field of optics and refraction. Basics of elementary optics and ocular optics are made easy by colorful representation.The topic of refraction can be mastered by reading this book as the reader can understand and correct the most difficult type of refractive errors with ease. Chapters on errors of accommodation and convergence are elaborated in lucid manner for better understanding of the readers.Managing binocular muscular balance anomalies is also explained under refractionReaders will be in the zone of comfort to treat all types of refractive anomalies once they go through .Art of optical correction of refractive errors can be mastered easily by reading the relevant chapters in .Prescribing and fitting of contact lenses will be a lot easier for the readers, especially in difficult corneal ectatic conditions, once they go through the chapters on contact lenses.Refractive surgical procedures are explained in an illustrative manner for comprehensive understanding of the facts.Uniqueness of this book is in which most appropriate answers to various clinical problems are explained in a simple and lucid manner.

optics refraction

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Section III:

Section IV:

Section V:

Vision and Refraction

Visual Rehabilitation

Problem-based Learning

Illustrated

Textbook ofOptics and

Refractive Anomalies

CBS Publishers & Distributors Pvt Ltd

New Delhi • Bengaluru • Chennai • Kochi • Kolkata • MumbaiHyderabad • Jharkhand • Nagpur • Patna • Pune • Uttarakhand

Illustrated

Textbook ofOptics and

Refractive Anomalies

AK Jain DNB, MNAMS

Assistant ProfessorDepartment of Ophthalmology

Rama Medical CollegeHapur, Uttar Pradesh

ISBN: 978-93-86478-63-4

Copyright © Author and Publisher

First Edition: 2018

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means,electronic or mechanical, including photocopying, recording, or any information storage and retrieval systemwithout permission, in writing, from the author and the publisher.

Published by Satish Kumar Jain and Produced by Varun Jain for

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DisclaimerScience and technology are constantly changing fields. Newresearch and experience broaden the scope of information andknowledge. The author has tried his best in giving informationavailable to him while preparing the material for this book.Although all efforts have been made to ensure optimumaccuracy of the material, yet it is quite possible some errors mighthave been left uncorrected. The publisher, the printer and theauthor will not be held responsible for any inadvertent errors orinaccuracies.

Illustrated

Textbook of

Optics and

Refractive Anomalies

to

my beloved family membersfor their support, encouragement and love

Foreword

Optics and refraction is the foundation stone of ophthalmology and comprehensive knowledge of basics is essential in clinical practice.

Majority of patients in ophthalmic practice have refractive errors, henceevery ophthalmic personnel including ophthalmologist must be welltrained to manage the refractive errors perfectly.

I am honoured and feel proud to write the Foreword to this book entitledIllustrated Textbook of Optics and Refractive Anomalies, as I had gone throughthe book and found it to be very useful for BSc and MSc optometry studentsand equally excellent for medical undergraduate and ophthalmologypostgraduate students. This book is unique in the sense that it not only contains the basicconcepts related to ocular optics and various refractive anomalies but also the live illustrationof refraction methods. These illustrations of refraction give a clear image of real live reflexesseen during retinoscopy; hence students can understand the exact types of refractive errorand can easily neutralize them when they perform retinoscopy on patients. The chapters onrefractive surgery and low vision are very informative for ophthalmology postgraduate students.The language and text style is written in a very simple and crispy manner so that students canunderstand the basic concepts and reproduce them in examination. Section on problem-basedlearning is an exclusive representation in textbook of ophthalmology. Various footnotes andproblem-based learning are the strengths of this book, which make the clear road for theclinical application of knowledge by the students in their daily practice. I congratulate theauthor for this unique endeavour on optics and refraction and wish him all the success for thisbook.

Prof DJ Pandey MS

Ex-Head, Department of Ophthalmology, andin-charge, Eye Bank and Cornea Clinic

SN Medical College, Agra, Uttar Pradesh

Past President, UPSOS; Vice President, ACOINGovernor Awarded: Best Teacher Award

Refractive anomalies are one of the most common clinical problems encountered in the field of ophthalmology throughout the world and remain one of the difficult challenges to

understand, hence a deep knowledge for correction of refractive anomalies is a prerequisite forthe successful ophthalmic practice. Illustrated Textbook of Optics and Refractive Anomalies has beenwritten to provide the basic information about optics and refractive errors. This book is writtenin a simple, concise and lucid manner with supportive illustrations in the form of ray diagrams,figures and tables so that the reader can acquire the profound knowledge about the subject withthe help of diagrammatic representation of the respective topic.

This book comprises 5 sections including 18 chapters where each section contains thediagrammatic illustrations related to text for easy understanding of the students. Section I deals withthe basic concepts of optics and lenses including light and its various properties, refraction andreflection through various surfaces and various types of lenses used in relation to the human eye.Basic knowledge of light and optics is essential to master the skill of refraction. This section servesas the foundation stone for correction of refractive anomalies of the human eye.

Section II covers various refractive anomalies associated with the human eye. This sectionconsists of refractive status of the human eye in relation to not only the refractive errors but alsowith convergence and accommodation anomalies. This section also includes chapter onrefractive errors seen with binocular vision anomalies and also the management of suchrefractive errors. Section III consists of chapters on vision and all the possible methods toevaluate the vision in the human eye. Visual status and the possibility in the amount ofimprovement in visual status form the basis for refraction. Evaluation of visual status is an artwhich requires the thorough knowledge of the examiner about the vision and cooperation ofthe patient, hence expressive examination techniques have been explained in this chapter tomake it easy for readers. For mastering the art of refraction, optics of various kinds ofretinoscopes and refraction tools is explained in great detail.

Section IV deals with the visual rehabilitation related to the management of different kindsof refractive anomalies. Detailed retinoscopy methods and various reflexes encountered duringretinoscopy are also explained in simpler and illustrated manner. Chapter on retinoscopycontains the diagrams representing the actual reflexes seen in the patient’s eye, hence the readercan master the technique of retinoscopy by reading this book. Section V at the end containsproblem-based learning, where various problems related to refraction encountered duringpractice and the possible solutions have also been discussed in detail.

I hope this book will help teachers, residents, ophthalmologists and optometrists to widentheir knowledge about optics and refraction. The knowledge and information gained from thisbook will assist the readers to comprehend the basic concepts of optics and various refractionanomalies of the human eye.

I believe that careful review and evaluation can create this book a better one and there isalways scope of improvement. If there are mistakes and printing errors, please mail yourfeedback and suggestions to dramitjain75@gmail.com.

AK Jain

Preface

It is my great pleasure to express my gratitude to all those whose blessings and contribution have made this endeavour possible. First and foremost, I would like to thank God, the

‘Almighty’, who has provided me the strength to undertake this work and complete itsuccessfully.

I would like to express my sincere thanks to Prof DJ Pandey for writing the Foreword tothis book. I take pride in acknowledging the guidance of Prof AK Gupta (former Dean, MaulanaAzad Medical College, New Delhi), ICARE Eye Hospital and Postgraduate Institute, Noida,who has been so helpful and cooperative in giving his support at all times to achieve my goal.

I also thank all my teachers, colleagues and students from Santosh Medical College; NarinderMohan Hospital, Ghaziabad; Saraswati Medical College and Rama Medical College, Hapur;ICARE Hospital and Research Centre, Noida; and Sharp Sight Centre, Delhi; for their kindcooperation and valuable suggestions to complete this project. I am also thankful to Dr SparshGupta, Dr Ashish Mehta, Dr Vivek Chhimpa, Dr Vikrant Sharma, Dr Vivek Jain, Dr Swati Guptaand Dr Amil A for their help and cooperation.

My acknowledgements would be incomplete without thanking all my family members fortheir indubitable support, love and encouragement in all my endeavours. I owe my specialthanks to my wife Dr Seema and lovely sweet daughter Harshita Jain for her great patience,understanding and for giving me unlimited happiness and pleasure.

I would like to thank Mr Satish Kumar Jain (CMD), Mr Varun Jain (Director), CBS Publishers& Distributors, and their management team for the enthusiastic cooperation, professional skills,and suggestions and to finish this task in an impressive manner. I would like to take thisopportunity to thank Mr YN Arjuna (Senior Vice-President—Publishing, Editorial and Publicity), Mrs RituChawla (AGM Production), Mr Prasenjit Paul (copyeditor), Mr Ram Murti (graphic artist), Mr Neeraj Prasad(graphic artist) and Mr Vikrant Sharma (DTP operator) for preparing the book material in a press-ready form. My thanks go to artist Mr Sumit Sharma whose artistic representations createdthe magical illustrations.

Last but not the least I thank all my patients who make me knowledgeable enough to writethis book on optics and refractive anomalies.

AK Jain

Acknowledgments

Foreword by Prof DJ Pandey vii

Preface ix

Section I: Optics and Ophthalmic Lenses

1. Elementary Optics 3

2. Reflection and Refraction 26

3. Ophthalmic Lenses 38

Section II: Ocular and Refractive Anomalies

4. Optical System and Optical Defects of Human Eye 61

5. Refractive Anomalies 76

6. Binocular Vision and its Anomalies 105

7. Accommodation and its Anomalies 134

8. Convergence and its Anomalies 163

9. Binocular Muscle Co-ordination Anomalies 188

Section III: Vision and Refraction

10. Visual Perception 201

11. Retinoscope and Retinoscopy 248

Section IV: Visual Rehabilitation

12. Spectacles, Spectacle Lenses and Spectacle Lens Fitting 305

13. Contact Lens Optics, Design and Fitting 362

14. Contact Lens Specific Conditions, Complications and Maintenance 409

15. Refractive Surgery 463

16. Low Vision 521

Section V: Problem-based Learning

17. Problems Related to Refractive Errors and Presbyopia 563

18. Problems Related to Refraction, Post-refractive Corrections and Low Vision 582

Index 605

Contents