Visual Optics (Lectures in Optics, 4)

722 Pages·2022·43.413 MB·English

by  George Asimellis

LECTURES IN OPTICS
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This fourth volume of the series Lectures in Optics provides comprehensive coverage of Visual
Optics, which is the field of optics as applied to the function of the eye, a magnificent and highly
complicated optical system. The optics part of vision in a ‘well-performing’ eye pertains to the
effects responsible for formation and initial detection of the retinal image—the picture of the
world as it is projected onto the photosensitive layer of the eye, the retina.
The book presents the necessary concepts and definitions that explain retinal image properties,
including aspects such as visual acuity and color perception. It discusses the optics of the eye in
the presence of refractive errors such as myopia, hyperopia, and astigmatism, certain limitations
to vision such as accommodation and near vision, and effects of aging on vision such as
presbyopia and low vision. Finally, chapters devoted to ophthalmic optics and prismatic effects
provide in-depth coverage of the optics involved in the correction of refractive vision disorders.
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P.O. Box 10
Bellingham, WA 98227-0010
ISBN: 9781510622616
SPIE Vol. No.: PM291
George Asimellis
Visual Optics
LECTURES IN OPTICS
Volume 4

George Asimellis
By the Author

Lectures in Optics, Vol. 1, Introduction to Optics
Lectures in Optics, Vol. 2, Geometrical Optics
Lectures in Optics, Vol. 3, Wave Optics
Lectures in Optics, Vol. 4, Visual Optics
Lectures in Optics, Vol. 5, Ocular Imaging
Visual Optics
LECTURES IN OPTICS
Volume 4

George Asimellis
SPIE PRESS
Bellingham, Washington USA
Library of Congress Cataloging-in-Publication Data
Names: Asimellis, George, 1966- author.
Title: Visual optics / George Asimellis.
Description: Bellingham, Washington : SPIE Press, [2022] | Series: Lectures
in optics ; Vol. 4 | Includes bibliographical references and index.
Identifiers: LCCN 2020046082 (print) | LCCN 2020046083 (ebook) | ISBN
9781510622616 (paperback) | ISBN 9781510622623 (pdf)
Subjects: LCSH: Eye--Accommodation and refraction. | Visual acuity. |
Physiological optics.
Classification: LCC RE925 .A78 2021 (print) | LCC RE925 (ebook) | DDC
617.7/5--dc23
LC record available at https://lccn.loc.gov/2020046082
LC ebook record available at https://lccn.loc.gov/2020046083
Published by
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Copyright © 2022 Society of Photo-Optical Instrumentation Engineers (SPIE)
All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means without
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The content of this book reflects the work and thought of the author. Every effort has been made to publish reliable
and accurate information herein, but the publisher is not responsible for the validity of the information or for any
outcomes resulting from reliance thereon.
Printed in the United States of America.
First Printing.
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COVER IMAGE:
MACRO PHOTOGRAPHY OF A FLY EYE WITH SPHERICAL DROPS ACTING AS MAGNIFYING LENSES PROVIDING LOCAL
DETAIL OF THE OMMATIDIA.
GEORGE ASIMELLIS LECTURES IN OPTICS, VOL 4

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ABLE OF ONTENTS

Table of Contents .............................................................................................................................................................................. i
Foreword ............................................................................................................................................................................................. ix
Preface ................................................................................................................................................................................................. xi
Acknowledgments ............................................................................................................................................................... xiii
1 OPTICS OF THE EYE ....................................................................................................................1-1
1.1 The Foundations of Vision .............................................................................................................................................. 1-1
Our Understanding – The First Steps ........................................................................................................... 1-1
1.2 Retinal Image Formation ................................................................................................................................................. 1-2
The Eye versus the Photo Camera ................................................................................................................. 1-3
1.3 Image Perception and Encoding .................................................................................................................................. 1-7
1.4 Ocular Refraction ............................................................................................................................................................. 1-17
Cardinal Points .................................................................................................................................................... 1-17
Optical Power of the Human Eye ................................................................................................................ 1-20
1.5 Models of the Eye ............................................................................................................................................................ 1-22
From the Simplest to the Most Complicated ......................................................................................... 1-22
Schematic Eye Models ..................................................................................................................................... 1-25
Ray Tracing ........................................................................................................................................................... 1-28
1.6 Optics of the Eye Quiz ................................................................................................................................................... 1-32
2 REFRACTIVE ELEMENTS OF THE EYE ........................................................................................... 2-35
2.1 Cornea .................................................................................................................................................................................. 2-35
Corneal Shape ..................................................................................................................................................... 2-35
Corneal Structure and Physiology .............................................................................................................. 2-37
Corneal Optical Power ..................................................................................................................................... 2-42
Corneal Asphericity and Toricity .................................................................................................................. 2-46
Tear Film ................................................................................................................................................................ 2-53
2.2 Crystalline Lens ................................................................................................................................................................. 2-56
Crystalline Lens: Shape & Optical Properties ......................................................................................... 2-56
Refractive Indices in the Eye .......................................................................................................................... 2-59
2.3 Anterior Chamber Optics ............................................................................................................................................. 2-62
Purkinje Images .................................................................................................................................................. 2-62
Anterior Chamber .............................................................................................................................................. 2-67
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LECTURES IN OPTICS VOL 4
2.4 Optical Apertures and Axes in the Human Eye ................................................................................................... 2-69
The Necessity of the Diaphragm ................................................................................................................. 2-69
Iris and Pupil ........................................................................................................................................................ 2-69
Axes and Reference Points in the Human Eye ....................................................................................... 2-78
Angles in the Human Eye ............................................................................................................................... 2-85
2.5 The Transit of Light in the Human Eye ................................................................................................................... 2-90
Losses due to Reflection ................................................................................................................................. 2-91
The Complicated Nature of Reflection Coefficients ............................................................................ 2-93
Losses Due to Absorption .............................................................................................................................. 2-97
The Ultraviolet Radiation and the Eye ....................................................................................................... 2-99
Losses due to Scattering ...............................................................................................................................2-101
2.6 Refractive Elements of the Eye Quiz ...................................................................................................................... 2-108
2.7 Ocular Refraction & Eye Elements Summary ..................................................................................................... 2-116
3 VISUAL ACUITY .................................................................................................................... 3-123
3.1 Angular Expressions...................................................................................................................................................... 3-124
Viewing Angle ...................................................................................................................................................3-127
Resolution Limit and Resolving Power ...................................................................................................3-128
3.2 Diffraction, a Limit to Vision ...................................................................................................................................... 3-129
The Rayleigh Criterion ...................................................................................................................................3-130
Aberrations and Visual Acuity ....................................................................................................................3-133
Other Factors Affecting Visual Acuity ......................................................................................................3-137
3.3 Visual Acuity Charts ...................................................................................................................................................... 3-141
Historical Background ....................................................................................................................................3-141
The Snellen Optotype Geometry ...............................................................................................................3-145
Snellen Chart Limitations ..............................................................................................................................3-152
3.4 The Measurement of Visual Acuity ........................................................................................................................ 3-154
Visual Acuity Notation ...................................................................................................................................3-154
Pinhole Visual Acuity ......................................................................................................................................3-155
Expressions of Visual Acuity ........................................................................................................................3-159
Advanced Optotypes and Eye Charts ......................................................................................................3-162
The logMAR Metric and the ETDRS Charts ...........................................................................................3-165
The Visual Acuity Rating ...............................................................................................................................3-170
Other Vision Assessment Metrics..............................................................................................................3-171
Digital / Electronic Charts .............................................................................................................................3-173
3.5 Visual Acuity Quiz .......................................................................................................................................................... 3-175
3.6 Visual Acuity Summary ................................................................................................................................................ 3-180
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VISUAL OPTICS

4 OPTICS OF THE RETINA.......................................................................................................... 4-185
4.1 Retinal Structure, Geometry, and Optics ............................................................................................................. 4-185
Retinal Shape .....................................................................................................................................................4-188
Thickness and Layered Structure of the Retina ...................................................................................4-190
Field of View / Visual Field Mapping .......................................................................................................4-192
4.2 Photoreceptors ............................................................................................................................................................... 4-197
Cones and Rods ................................................................................................................................................4-197
Photoreceptor Pathways ...............................................................................................................................4-200
Fovea: the Center of Vision ..........................................................................................................................4-202
4.3 The Photonic Sensation .............................................................................................................................................. 4-203
Spectral Sensitivity...........................................................................................................................................4-204
Response to Luminance ................................................................................................................................4-205
Light and Dark Adaptation ..........................................................................................................................4-206
The Purkinje Shift .............................................................................................................................................4-210
Receptive Fields ................................................................................................................................................4-211
Ganglion Cell Excitation and Inhibition ..................................................................................................4-213
4.4 Photoreceptor Optics ................................................................................................................................................... 4-219
Optical Fiber Guidance ..................................................................................................................................4-219
Stiles–Crawford Effect ....................................................................................................................................4-220
4.5 Digital Signal and Analysis ......................................................................................................................................... 4-222
The Retina Display ...........................................................................................................................................4-224
Sampling and Digital Sensation .................................................................................................................4-225
Digital Resolution of the Human Eye? Is it 240 Mpixel? ................................................................4-232
4.6 Retina Quiz ....................................................................................................................................................................... 4-233
4.7 Retina Summary ............................................................................................................................................................. 4-238
5 COLOR PERCEPTION .............................................................................................................. 5-241
5.1 Color in Optics ................................................................................................................................................................ 5-241
Primary Colors ...................................................................................................................................................5-247
Color Properties ................................................................................................................................................5-248
Additive & Subtractive Colors ....................................................................................................................5-249
Color Spaces ......................................................................................................................................................5-251
5.2 Perception of Colors in the Human Eye ............................................................................................................... 5-260
The Three Cone Types ...................................................................................................................................5-260
Process Theories ...............................................................................................................................................5-263
Subjectivity of Color Perception ................................................................................................................5-271
Color Vision in Other Species .....................................................................................................................5-273
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LECTURES IN OPTICS VOL 4
5.3 Color Vision Deficiency ............................................................................................................................................... 5-276
Classification of Color Vision Deficiencies .............................................................................................5-277
Inheritance of Color Vision Deficiency ....................................................................................................5-285
Acquired Color Vision Deficiencies ..........................................................................................................5-289
5.4 Testing Color Vision Deficiency ............................................................................................................................... 5-291
Lantern Tests ......................................................................................................................................................5-293
Pseudoisochromatic Tests ............................................................................................................................5-293
Arrangement Tests ..........................................................................................................................................5-301
The Anomaloscope .........................................................................................................................................5-306
Computerized CVD tests ...............................................................................................................................5-310
5.5 Color Perception Quiz.................................................................................................................................................. 5-312
5.6 Color Perception Summary ....................................................................................................................................... 5-319
6 AMETROPIAS........................................................................................................................ 6-323
6.1 Focusing in the Eye ....................................................................................................................................................... 6-324
Vergence and Effective Power ....................................................................................................................6-324
The Circle of Least Confusion .....................................................................................................................6-326
The Near and Far Points ................................................................................................................................6-327
Depth of Field and Depth of Focus ..........................................................................................................6-329
Depth of Field and Range of Clear Vision .............................................................................................6-334
6.2 Emmetropia ...................................................................................................................................................................... 6-335
Axial Length and Focal Length ...................................................................................................................6-335
Retinal Image Size in the Emmetropic Eye ............................................................................................6-337
6.3 Ametropia ≠ Emmetropia .......................................................................................................................................... 6-339
Chromatic Aberration and Vision ..............................................................................................................6-339
Monochromatic Aberrations .......................................................................................................................6-342
6.4 Myopia and Hyperopia ................................................................................................................................................ 6-343
Myopia ..................................................................................................................................................................6-343
Hyperopia ............................................................................................................................................................6-348
Defocus, Axial Length, and Corneal Curvature ....................................................................................6-354
6.5 Effects of Ametropia ..................................................................................................................................................... 6-357
Cardinal Points in Ametropia ......................................................................................................................6-357
Retinal Image Size and Blur in Uncorrected Ametropia ..................................................................6-357
Effect of Ametropias on Visual Acuity .....................................................................................................6-361
Effect of Ametropias on Depth of Focus ................................................................................................6-363
6.6 Spectacle Correction of Myopia and Hyperopia .............................................................................................. 6-367
Correction of Myopia: Optical Principles ...............................................................................................6-367
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VISUAL OPTICS

Correction of Hyperopia: Principles .........................................................................................................6-368
The Challenge of Hyperopia Correction.................................................................................................6-370
The Correction of Aphakia ...........................................................................................................................6-371
Knapp’s Rule ......................................................................................................................................................6-372
6.7 Ametropia Quiz .............................................................................................................................................................. 6-374
6.8 Ametropia Summary .................................................................................................................................................... 6-381
7 ACCOMMODATION AND PRESBYOPIA ..................................................................................... 7-383
7.1 The Nature of Accommodation ............................................................................................................................... 7-383
The Need to Adapt to Shorter Distances ...............................................................................................7-383
Accommodation Theories ............................................................................................................................7-384
Variable Lenticular Power .............................................................................................................................7-386
7.2 Magnitude and Amplitude of Accommodation ............................................................................................... 7-391
Magnitude of Accommodation..................................................................................................................7-391
Amplitude of Accommodation ...................................................................................................................7-393
Measurement of the Amplitude of Accommodation .......................................................................7-397
7.3 Classification of Accommodation ........................................................................................................................... 7-399
Classification on the Basis of Measurement .........................................................................................7-399
Classification of Involuntary Accommodation .....................................................................................7-400
Pseudoaccommodation ................................................................................................................................7-403
7.4 Anomalies of Accommodation ................................................................................................................................ 7-404
7.5 Accommodation and Spectacle Wear ................................................................................................................... 7-406
Influence of Refractive Error ........................................................................................................................7-406
Accommodation in the Uncorrected and Corrected Hyperope ...................................................7-408
Accommodation in the Uncorrected and Corrected Myope .........................................................7-412
7.6 Convergence and Accommodation Effects ........................................................................................................ 7-418
Convergence and Spectacle Wear ............................................................................................................7-421
7.7 Presbyopia ........................................................................................................................................................................ 7-425
Understanding the Problem ........................................................................................................................7-425
Physiological Etiology ....................................................................................................................................7-426
The Add Power ..................................................................................................................................................7-427
Presbyopia Classification ..............................................................................................................................7-431
7.8 The Management of Presbyopia ............................................................................................................................. 7-431
Spectacle Correction for Presbyopia .......................................................................................................7-432
Monovision .........................................................................................................................................................7-434
Contact Lenses for Presbyopia ...................................................................................................................7-435
Presbyopia Surgical Management Options ..........................................................................................7-439
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