Image Modeling of the Human Eye

Transcription

1 Image Modeling of the Human Eye Rajendra Acharya U Eddie Y. K. Ng Jasjit S. Suri Editors ARTECH H O U S E BOSTON LONDON artechhouse.com

2 Contents Preface xiiii CHAPTER1 The Human Eye Basic Ocular Anatomy and Physiology The Cornea The Aqueous Humor The Iris TheLens The Vitreous Humor The Sclera 1 Cornea Retina Structure of the Cornea Structure of the Retina Organization of Neuronal Cell Layers Path of Visual Signals Anterior Segment Abnormalities Keratoconus Corneal Ulcer Fuchs'Dystrophy Pterygium and Pingueculae Scleritis Uveitis Corneal Haze Cataracts Posterior Segment Abnormalities Diabetic Retinopathy Macular Degeneration Retinal Detachment Floaters Glaucoma References 5 CHAPTER 2 Introduction to Imaging Optics Properties of Light 7 V

3 VI Contents Refraction Angle of Refraction Critical Angle and Total Internal Reflection Loss of Energy Dispersion of Light into a Spectrum Redirection of the Light Ray Basic Prism Optical Wedge Reflecting Surfaces The Reflected Image Double Reflection Practical Prisms Amici (Roof Edge) Prism Schmidt Prism Penta Prism Cube Beam Splitters Lateral Displacement Beam Splitters Basic Imaging (First-Order Paraxial Optics) Cardinal (Gauss) Points and Focal Length Image Formation Using a Positive Lens Optical Axis, Chief Rays, and Marginal Rays Aperture Stop Iris Entrance and Exit Pupils Vignetting Real Images Physical Devices and Their Effects Aperture and Lens Hood Obstruction Virtual Images Converting a Virtual Image into a Real Image Minimum and Maximum Separation Between Lenses Virtual Image at Infinity Vignetting Due to Eye Position Controlled Size Imaging Adding an Objective (Convex) Lens to Increase Image Size Multiple Lens Imaging A Practical Three-Lens System Lasers Generation of a Laser 66 References 69 CHAPTER Eye Imaging Systems 71.1 Computed Tomography Principle Applications 76

4 .1. Advantages.1.4 Limitations.2 Confocal Laser Scanning Microscopy.2.1 Principle.2.2 Applications.2. Advantages.2.4 Limitations. Magnetic Resonance Imaging..1 Principle..2 Applications.. Advantages..4 Limitations.4 Optical Coherence Tomography.4.1 Principles.4.2 Applications.4. Advantages.4.4 Limitations.5 Ultrasound Imaging.5.1 Principle.5.2 Color Doppler Imaging.5. Applications.5.4 Advantages.5.5 Limitations.6 Discussion.7 Conclusions References Automatic Identification of Anterior Segment Eye Abnormalities Optical Images 4.1 Introduction 4.2 Data Acquisition 4. Preprocessing 4..1 Histogram Equalization 4..2 Binarization 4.4 Features Used for the Classification Big Ring Area Small Ring Area 4.4. Homogeneity BW Morph 4.5 Artificial Neural Network-Based Classifier Backpropagation Learning Algorithm 4.6 Results 4.7 Discussion 4.8 Conclusions References

5 VIII Contents CHAPTER 5 Identification of Different Stages of Diabetic Retinopathy Using Retinal Optical Images Introduction Computer Methods and Theory Imaging Techniques Features System Description Gaussian Mixture Model for Classification Statistics of System Discussion Conclusions 128 References 128 CHAPTER 6 Computer-Based Detection of Diabetes Maculopathy Stages Using Higher-Order Spectra Introduction Nonclinically Significant Maculopathy Clinically Significant Maculopathy Data Acquisition and Processing Preprocessing of Image Data Feature Extraction Higher-Order Spectra (HOS) Fuzzy Classifier Results Discussion Conclusions 142 Acknowledgments 14 References 14 CHAPTER 7 Algorithms for Detecting Glaucomatous Structural Changes in the Optic Nerve Head Anatomy of the Eye and Pathophysiology of Glaucoma Anatomy of the Eye Pathophysiology of Glaucoma Morphological Changes in the ONH Region in Glaucoma Optic Disc Configuration Retinal Nerve Fiber Layer Defects Parapapillary Atrophy and Optic Disc Hemorrhages Confocal Scanning Laser Ophthalmoscope for ONH Analysis Principle of Confocal Microscopy Measuring Optic Disc Stereometrie Parameters from the CSLO Optic Disc Topographs Algorithms for Detecting Glaucomatous Damage of the ONH Algorithms for Detecting Glaucomatous Progression in the ONH 162

6 Contents IX Essential Qualities of the Computational and Statistical Methods Applied for Detecting Glaucomatous Structural Changes Stereometrie Parameter-Based Progression Analysis Topographie Change Analysis (TCA) Nonparametric Permutation Tests Progression Analysis Summary 181 Acknowledgments 184 References 184 CHAPTER 8 Fractal Measures for Fungal Keratitis Diagnosis Using a White-Light Confocal Microscope Introduction A Computational Framework for Identifying Filamentous Fungi in Corneal Confocal Images Fungal Feature Extraction Fractal Dimension Based Feature Metrics Image Classification Results Conclusions and Future Work 198 Acknowledgments 201 References 201 CHAPTER 9 Vessel Detection Experiments Using a Gaussian Matched Filter Spatial Filters for the Detection of Blood Vessels Estimation of Filter Parameters True Versus False Vessels Some Filter Parameters Best Rotation for Filter Band Selection of the Retinal Image Best Threshold for Segmenting the Vessel Image Summary 21 References 214 CHAPTER10 Detection of Retinal Blood Vessels Using Gabor Filters Introduction Retinopathy Detection of Retinal Blood Vessels Methods Gabor Filters for the Detection of Oriented Patterns Procedure for the Detection of Retinal Blood Vessels Experiments and Results Data Set of Retinal Images and Preprocessing Single-Scale Filtering and Analysis Multiscale Filtering and Analysis 222

7 X Contents 10.4 Discussion and Conclusions 22 Acknowledgments 224 References 224 CHAPTER11 Finite Element Simulation of the Eye Structure with Bioheat Analysis: Two- and Three-Dimensional Ocular Surface Temperature Profiles Introduction Previously Developed Models Development of the Human Eye Model Mathematical Description Governing Equation Boundary Conditions Additional Assumptions Numerical Methodology Steady-State Temperature Distribution Sensitivity Analysis Effects of Lens Thermal Conductivity Effects of Blood Convection Coefficient Effects of Ambient Convection Coefficient Effects of Blood Temperature Effects of Ambient Temperature Effects of Tear Evaporation Rate Summary from Sensitivity Analysis Study Effects of EM Wave Exposure on the Human Eye Governing Equations and Boundary Conditions Results and Discussion Summary 249 References 250 CHAPTER 12 Variations of the Corneal Surface Temperature with Contact Lens Wear Introduction A Brief History of Contact Lens Tear Film and Tear Evaporation Contact Lens and Corneal Surface Temperature The Contact Lens Model Model Development Governing Equation and Boundary Conditions Numerical Methodology Numerical Predictions and Analysis Steady-State Analysis Transient Analysis Summary and Discussion 265 References 266

8 XI CHAPTER1 An Axisymmetric Boundary Element Model for Bioheat Transfer in the Human Eye Introduction The Axisymmetric Human Eye Model The Governing Equation The Axisymmetric Boundary Element Method Numerical Results and Analysis Sensitivity Analysis Effects of Lens Thermal Conductivity Effects of Ambient Temperature Effects of Blood Temperature Effects of Ambient Convection Coefficient Effects of Blood Convection Coefficient Effects of Tear Evaporation Discussion and Conclusions 282 References 284 CHAPTER14 Simulation of Aqueous Humor Circulation Inside the Human Eye Introduction The Human Eye Model Governing Equations Boundary Conditions Aqueous Humor Hydrodynamics Numerical Methodology Results and Analysis The Effects of Aqueous Humor Circulation The Effects of Eye Orientation Discussion Conclusions 298 References 299 CHAPTER 15 Clinical Implications for Thermography in the Eye World: A Short History of Clinical Ocular Thermography Introduction Early Techniques of Ocular Temperature Assessment Noncontact Ocular Temperature Measurement Converting Radiation Readings to Temperatures Ocular Thermography TypicalOST The Influence of the Environment on OST Individual Variations in OST Ocular Disease and Ocular Temperature Summary 14 References 15

9 XII Contents CHAPTER 16 Temperature Measurement of the Anterior Eye During Hydrogel Contact Lens Wear 16.1 Introduction 16.2 Method Study Population Study Design and Procedure Data Acquisition and Analysis 16. Results 16.4 Discussion Possible Clinical Relevance 16.5 Conclusions References CHAPTER 17 Variations of C >cular Surface Temperature with Different Age Groups 17.1 Introduction Variations of Ocular Surface Temperature with Age Clinical Applications 17.2 Methodology Equipment Specifications Reference Emitter Technique Test Subjects 17. Results and Discussion Effectiveness of Infrared Cameras in Ocular Surface Thermography 17.4 Conclusions Acknowledgments References About the Editors List of Contributors ndex