Clinical Optics

Clinical Optics is intended primarily for use by optometry students, though it could also prove useful for the training of optometric technicians and dispensing opticians. This book is organized into thirteen chapters. These chapters cover most aspects of ophthalmic optics or clinical optics including the design and dispensing of eyewear, the types for lenses suitable for correcting high refractive errors, the optical principles governing low vision lenses and the importance of absorptive lenses and lens coatings for eye protection against radiation.
This book will be of interest to optometry students and to those involved in the training of optometric technicians and dispensing opticians.

Contents

Preface

Introduction. Sign Convention, Nomenclature, and Notation

0.1 Sign Convention

0.2 Nomenclature

0.3 Notation

Chapter One Ophthalmic Lens Materials

Glass

1.1 History of Glassmaking

1.2 The Development of Optical Glass

1.3 The Manufacture of Optical Glass

1.4 Varieties of Optical Glass

1.5 Desirable Characteristics and Defects of Optical Glass

Plastic Materials

1.6 Introduction

1.7 Manufacturing Processes

1.8 Development of Optical Plastics

1.9 Manufacture of Plastic Lenses

1.10 Optical and Physical Properties of Plastic Lenses

The Strength of Lens Materials

1.11 FDA Policies

1.12 The Strength of Glass

1.13 Methods of Tempering Glass Lenses

1.14 Impact Resistance of Plastic Lenses

1.15 Lenses for Occupational and Educational Use

References

Questions

Chapter Two Characteristics of Ophthalmic Lenses

Physical Characteristics

2.1 Curvature

2.2 Surfaces of Revolution

2.3 Relationship between Curvature and Refracting Power of a Surface

2.4 The Lens Measure

2.5 Lens Form: Spherical Lenses

2.6 Lens Form: Cylindrical and Toric Lenses

2.7 Lens Blanks and Base Curves

2.8 Specification of Cylinder Axes

2.9 Prescription Writing and Transposition

Optical Characteristics

2.10 Basic Terminology

2.11 Image Formation by a Spherical Lens

2.12 Image Formation by Cylindrical and Toric Lenses

2.13 Terminology and Basic Concepts Regarding Image Formation by a Lens

2.14 Dimensional Aspects of the Conoid of Sturm

2.15 Misconceptions Concerning Astigmatic Image Formation

2.16 The Spherical Equivalent

2.17 Power in an Oblique Meridian of a Cylindrical Lens

2.18 Power in an Oblique Meridian of aToric Lens

2.19 Obliquely Crossed Cylinders

2.20 Astigmatism due to Lens Tilt

2.21 The Maddox Rod

References

Questions

Chapter Three. Power Specification and Measurement

Power Specification

3.1 Introduction

3.2 Approximate Power

3.3 Back Vertex Power

3.4 Front Vertex Power, or Neutralizing Power

3.5 Equivalent Power

3.6 Effective Power

Power measurement

3.7 Hand Neutralization

3.8 The Lensometer

3.9 Lensometer Calibration, Alignment, and Measurement Errors

3.10 Projection Lensometers

3.11 Automatic Lensometers

Relationships Between Lens Power and Lens Thickness

3.12 The Sagitta Formula

3.13 Formula Relating Power to Center Thickness and Edge Thickness

3.14 Thickness Calculations for Cylindrical and Sphero-cylindrical Lenses

Reference

Questions

Chapter Four

Ophthalmic Prisms and Decentration

4.1 Terminology

4.2 Refracting Power of a Prism

4.3 Specification of the Power of an Ophthalmic Prism

4.4 Relationship between Refracting Angle and Angle of Deviation

4.5 Effects of Prisms on Movements of the Eyes

4.6 Prentice's Rule

4.7 Oblique Prismatic Effects

4.8 Obliquely Crossed Prisms

4.9 Effective Power of a Prism in an Oblique Meridian

4.10 Specification of Prismatic Effects: The Major Reference Point

4.11 Specification of Lens and Frame Sizes

4.12 Prismatic Power and Thickness

4.13 Thickness of a Lens/Prism

4.14 Prismatic Effects of Cylindrical Lenses

4.15 Decentration

4.16 Effects of Prisms on the Eyes

4.17 Effectivity of a Prism

4.18 Risley Prisms

4.19 Fresnel Press-on Prisms

References

Questions

Chapter Five. The Correction of Ametropia

5.1 The Schematic Eye

5.2 Emmetropia and Ametropia

5.3 The Far and Near Points of Accommodation

5.4 The Correction of Spherical Ametropia

5.5 Range and Amplitude of Accommodation

5.6 Spectacle Refraction versus Ocular Refraction

5.7 Spectacle Accommodation versus Ocular Accommodation

5.8 Accommodation and Effectivity in Anisometropia

5.9 Accommodation and Effectivity in Astigmatism

5.10 Retinal Image Size in Uncorrected Ametropia

5.11 Retinal Image Size in Corrected Ametropia

References

Questions

Chapter Six. Aberrations and Ophthalmic Lens Design

Introduction

6.1 Laws of Geometrical Optics

Chromatic Aberration and Achromatic Lenses

6.2 Chromatic Aberration

6.3 Chromatic Dispersion

6.4 Chromatic Aberration in Prisms

6.5 Achromatic Prisms

6.6 Chromatic Aberration in Lenses

6.7 Achromatic Lenses

The Monochromatic Aberrations

6.8 Spherical Aberration

6.9 Coma

6.10 Oblique Astigmatism

6.11 Curvature of Image

6.12 Distortion

Principles of Lens Design

6.13 Introduction

6.14 Lens Design Variables

6.15 Design Assumptions

6.16 The Base Curve of a Lens

History and Evolution of Lens Design

6.17 Spherical Lenses

6.18 Sphero-Cylindrical Lens Design

6.19 Negative versus Positive Toric Lenses

6.20 Design of High Plus Lenses

The Optometrists Role in Lens Design

6.21 Changes in the Optical Industry and in ANSI Standards

6.22 Base Curve Specification

References

Questions

Chapter seven. Absorptive Lenses and Lens Coatings

Effects of Radiation on the Eye

7.1 The Nature of Light

7.2 The Visible Spectrum

7.3 Classification of Radiation Effects

7.4 Concentration of Radiant Energy by the Eye

7.5 Absorption of Radiation by the Ocular Tissues

7.6 Effects of Ultraviolet Radiation

7.7 Effects of Infrared Radiation

7.8 The Effects of Visible Radiation

7.9 Other Forms of Radiation

7.10 Recommended Levels of Retinal Illumination

Absorptive Lenses

7.11 Reflection, Absorption, and Transmission

7.12 Opacity

7.13 Density

7.14 Methods of Manufacturing Absorptive Lenses

7.15 Categories of Absorptive Lenses and Specification of Transmission

7.16 General-Wear Lenses Absorbing the Spectrum Evenly

7.17 Lenses That Selectively Absorb Ultraviolet Radiation While Transmitting the Visible Spectrum in a

Uniform Manner

7.18 Lenses That Selectively Absorb Both Ultraviolet and Infrared Radiation While Absorbing a Substantial

Amount of Visible Radiation in a Relatively Uniform Manner

7.19 Lenses That Selectively Absorb Portions of the Visible Spectrum

7.20 Absorptive Lenses Designed for Occupational Use

7.21 Photochromic Lenses

7.22 Lens Thickness and Transmission

7.23 Prescribing Absorptive Lenses

7.24 Miscellaneous Absorptive Lenses

Lens Reflections and Coatings

7.25 Refleaions from Spectacle Lens Surfaces

7.26 Types of Surface Reflections

7.27 Methods of Controlling Surface Reflections

7.28 Antireflective Coatings

7.29 Optical Principles of Antireflective Coatings

7.30 Production of Antireflective Coatings

7.31 Reflections Annoying to an Observer

References

Questions

Chapter Eight. Multifocal Lenses

Physical Characteristics

8.1 History and Development of Multifocal Lenses

8.2 Fused Bifocal Lenses

8.3 One-Piece Bifocal Lenses

8.4 Double-Segment Bifocals

8.5 "Minus Add" Bifocal

8.6 Trifocal Lenses

8.7 Plastic Multifocal Lenses

Multifocal Lens Manufacturing Processes

8.8 Glass Multifocals

8.9 Plastic Multifocals

Optical Principles of Multifocal Lens Design

8.10 Powers of the Distance and Reading Portions

8.11 One-Piece Bifocals

8.12 Fused Bifocals

Performance Characteristics

8.13 Vertical Placement of the Optical Center of the Segment

8.14 Lateral Placement of the Optical Center of the Segment

8.15 Differential Displacement (Image Jump)

8.16 The Zone of Confusion

8.17 Differential Displacement at the Reading Level

8.18 Total Displacement at the Reading Level

8.19 Transverse Chromatic Aberration

Clinical Considerations

8.20 Theories of Bifocal Selection

8.21 Segment Size and Shape

8.22 Horizontal Prismatic Effects

8.23 Differential Vertical Prismatic Effects at the Reading Level

8.24 Ordering and Dispensing Bifocals

8.25 Verification of Bifocals

8.26 Prescribing and Fitting Double-Segment Bifocals

8.27 Prescribing and Fitting Trifocals

Invisible bifocals and progressive addition Lenses

8.28 Invisible Bifocals

8.29 Blended Bifocals

8.30 Progressive Addition Lenses

8.31 Patient Selection and Dispensing Considerations

References

Questions

Chapter Nine. Eyewear Design and Dispensing

Spectacle Frames and Mountings

9.1 Historical Introduction

9.2 Modern Frames and Mountings

9.3 Metal Frame and Mounting Materials

9.4 Plastic Frame Materials

9.5 Bridge and Temple Styles

Frame Selection and Ordering Materials

9.6 Measuring Interpupillary Distance

9.7 Frame Selection

9.8 Fitting Principles

9.9 Frame Alignment

9.10 Frame and Mounting Specifications

9.11 Lateral Placement of Optical Centers

9.12 Vertical Placement of Optical Centers

9.13 Centering Problems and Solutions

9.14 Bifocal Segment Inset

9.15 Prescription Order Forms

Verification and Dispensing

9.16 Verification

9.17 Dispensing and Adjusting

References

Questions

Chapter Ten. Anisometropia and Aniseikonia

Anisometropia

10.1 Problems Resulting from Anisometropia

10.2 Horizontal Prismatic Effects

10.3 Differential Vertical Prismatic Effects at the Reading Level

Aniseikonia

10.4 Introduction

10.5 Etiology of Aniseikonia

10.6 Significance of Aniseikonia

10.7 The Spectacle Magnification Formula

10.8 Clinical Application of the Spectacle Magnification Formula

10.9 Comparison of Spectacle and Contact Lens Magnification

10.10 Spectacle Magnification in Astigmatism

10.11 Relative Spectacle Magnification

10.12 Relative Spectacle Magnification in Axial Ametropia

10.13 Relative Spectacle Magnification in Refractive Ametropia

10.14 Relative Spectacle Magnification in Astigmatism

10.15 The Dilemma of Relative Spectacle Magnification

10.16 Clinical Considerations in Anisometropia and Astigmatism

Prescribing to Eliminate or Minimize Induced Aniseikonia

10.17 Indications of the Presence of Aniseikonia

10.18 Measurement of Image Size Differences

10.19 Estimating the Amount of Aniseikonia

10.20 Avoiding or Minimizing Induced Aniseikonia

10.21 Prescribing and Lens Design

10.22 The Use ofEikonic Lenses in Fit-Over Form

10.23 Frame Selection for Eikonic Lenses

10.24 Aniseikonia: Clinical Considerations in Anisometropia and Astigmatism

References

Questions

Chapter Eleven. Lenses for High Refractive Errors

Lenses for Aphakia and High Hyperopia

11.1 Management of the Cataract Patient

11.2 Optical Consequences of Cataract Surgery

11.3 Predicting the Power of an Aphakic Lens

11.4 Problems with Aphakic Spectacles

11.5 Parameters of Aphakic Lenses

11.6 Aphakic Lens Design

11.7 Frames for Aphakic Lenses

11.8 The Unilateral Aphakic

11.9 Determining^the Final Aphakic Prescription

11.10 The High Hyperope

Lenses for High Myopia

11.11 Problems Caused by High Minus Lenses

11.12 Minimizing Edge Thickness

11.13 Minimizing Edge Reflections

11.14 Lenticular Lenses

11.15 Fresnel Press-on Lenses

References

Questions

Chapter Twelve. Optical Principles of Lenses for Low Vision

12.1 Methods of Providing Magnification

Optical Aids for Distance Vision

12.2 Afocal Telescopes

12.3 Headborne Telescopic Systems

12.4 Nonprescription Telescopes

Optical Aids for Near Vision

12.5 Microscopic Lenses

12.6 Telescopic Lenses for Near Vision

12.7 Hand Magnifiers

12.8 Stand Magnifiers

12.9 The Paperweight Magnifier

References

Questions

Chapter Thirteen. Optics of Contact Lenses

Basic Contact Lens Optics

13.1 The Contact Lens as a Thick Lens

13.2 The Effective Power of a Contact Lens

13.3 Calibration of the Keratometer

The Contact Lens/Eye Optical System

13.4 The Contact Lens on the Eye

13.5 Over-refraction

13.6 Contact Lenses and Corneal Astigmatism

13.7 Fitting Steeper or Flatter Than the Cornea

13.8 The Optics of Bifocal Contact Lenses

13.9 Residual Astigmatism and Its Correction

13.10 Magnification Effects of Contact Lenses

Effects of Contact Lenses on Binocular Vision

13.11 Accommodative Demand

13.12 Accommodative Convergence

13.13 Prismatic Effects

13.14 Prescribing Prism in a Contact Lens

Aberrations and Field of View

13.15 Aberrations

13.16 Field of View

Aphakia

13.17 Aphakic Contact Lenses

Instrumentation

13.18 The Radiuscope

References

Questions

Answers to Questions

Index