Adaptive Optics for Vision Science. Principles, Practices, Design, and Applications

Transcription

1 Adaptive Optics for Vision Science Principles, Practices, Design, and Applications Edited by JASON PORTER, HOPE M. QUEENER, JULIANNA E. LIN, KAREN THORN, AND ABDUL AWWAL m WILEY- INTERSCIENCE A JOHN WILEY & SONS, INC., PUBLICATION

2 Contents FOREWORD ACKNOWLEDGMENTS CONTRIBUTORS xvii xxi xxiii PART ONE INTRODUCTION 1 1 Development of Adaptive Optics in Vision Science and Ophthalmology 3 David R. Williams and Jason Porter 1.1 Brief History of Aberration Correction in the Human Eye Vision Correction Retinal Imaging Applications of Ocular Adaptive Optics Vision Correction Retinal Imaging 11 PART TWO WAVEFRONT MEASUREMENT AND CORRECTION 31 2 Aberration Structure of the Human Eye 33 Pablo Artal, Juan M. Bueno, Antonio Guirao, and Pedro M. Prieto 2.1 Introduction Location of Monochromatic Aberrations Within the Eye 34 V

3 vi 2.3 Temporal Properties of Aberrations: Accommodation and Aging Effect of Accommodation on Aberrations and Their Correction Aging and Aberrations Chromatic Aberrations Longitudinal Chromatic Aberration Transverse Chromatic Aberration Interaction Between Monochromatic and Chromatic Aberrations Off-Axis Aberrations Peripheral Refraction Monochromatic and Chromatic Off-Axis Aberrations Monochromatic Image Quality and Correction of Off-Axis Aberrations Statistics of Aberrations in Normal Populations Effects of Polarization and Scatter Impact of Polarization on the Ocular Aberrations Intraocular Scatter 55 Wavefront Sensing and Diagnostic Uses 63 Geunyoung Yoon 3.1 Wavefront Sensors for the Eye Spatially Resolved Refractometer Laser Ray Tracing Shack-Hartmann Wavefront Sensor Optimizing a Shack-Hartmann Wavefront Sensor Number of Lenslets Versus Number of Zernike Coefficients Trade-off Between Dynamic Range and Measurement Sensitivity Focal Length of the Lenslet Array Increasing the Dynamic Range of a Wavefront Sensor Without Losing Measurement Sensitivity Calibration of a Wavefront Sensor Reconstruction Algorithm System Aberrations Summary 79

4 vii 4 Wavefront Correctors for Vision Science 83 Nathan Doble and Donald T. Miller 4.1 Introduction Principal Components of an AO System Wavefront Correctors Wavefront Correctors Used in Vision Science Macroscopic Discrete Actuator Deformable Mirrors Liquid Crystal Spatial Light Modulators Bimorph Mirrors Microelectromechanical Systems Performance Predictions for Various Types of Wavefront Correctors Description of Two Large Populations Required Corrector Stroke Discrete Actuator Deformable Mirrors Piston-Only Segmented Mirrors Piston/Tip/Tilt Segmented Mirrors Membrane and Bimorph Mirrors Summary and Conclusion Control Algorithms 119 Li Chen 5.1 Introduction Configuration of Lenslets and Actuators Influence Function Measurement Spatial Control Command of the Wavefront Corrector Control Matrix for the Direct Slope Algorithm Modal Wavefront Correction Wave Aberration Generator Temporal Control Command of the Wavefront Corrector Open-Loop Control Closed-Loop Control Transfer Function of an Adaptive Optics System Adaptive Optics Software for Vision Research 139 Ben Singer 6.1 Introduction Image Acquisition Frame Rate Synchronization Pupil Imaging 141

5 viii 6.3 Measuring Wavefront Slope Setting Regions of Interest Issues Related to Image Coordinates Adjusting for Image Quality Measurement Pupils Preparing the Image Centroiding Aberration Recovery Principles Implementation Recording Aberration Displaying a Running History of RMS Displaying an Image of the Reconstructed 148 Wavefront 6.5 Correcting Aberrations Recording Influence Functions Applying Actuator Voltages Application-Dependent Considerations One-Shot Retinal Imaging Synchronizing to Display Stimuli Selective Correction Conclusion Making Programmers Happy Making Operators Happy Making Researchers Happy Making Subjects Happy Flexibility in the Middle 153 Adaptive Optics System Assembly and Integration 155 Brian J. Bauman and Stephen K. Eisenbies 7.1 Introduction First-Order Optics of the AO System Optical Alignment Understanding Penalties for Misalignments Optomechanics Common Alignment Practices Sample Procedure for Offline Alignment AO System Integration Overview Measure the Wavefront Error of Optical Components Qualify the DM 175

6 ix Qualify the Wavefront Sensor Check Wavefront Reconstruction Assemble the AO System Boresight FOVs Perform DM-to-WS Registration Measure the Slope Influence Matrix and Generate Control Matrices Close the Loop and Check the System Gain Calibrate the Reference Centroids 185 System Performance Characterization 189 Marcos A. van Dam 8.1 fntroduction Strehl Ratio Calibration Error Fitting Error Measurement and Bandwidth Error Modeling the Dynamic Behavior of the AO System Computing Temporal Power Spectra from the Diagnostics Measurement Noise Errors Bandwidth Error Discussion 8.6 Addition of Wavefront Error Terms LT THREE RETINAL IMAGING APPLICATIONS 203 Fundamental Properties of the Retina Ann E. Eisner 9.1 Shape of the Retina 9.2 Two Blood Supplies 9.3 Layers of the Fundus 9.4 Spectra 9.5 Light Scattering 9.6 Polarization 9.7 Contrast from Directly Backscattered or Multiply Scattered Light 9.8 Summary Strategies for High-Resolution Retinal Imaging 235 Austin Roorda, Donald T. Miller, and Julian Christou 10.1 Introduction 235

7 x 10.2 Conventional Imaging Resolution Limits of Conventional Imaging Systems Basic System Design Optical Components Wavefront Sensing Imaging Light Source Field Size Science Camera System Operation Scanning Laser Imaging Resolution Limits of Confocal Scanning Laser Imaging Systems Basic Layout of an AOSLO Light Path Light Delivery Wavefront Sensing and Compensation Raster Scanning Light Detection Frame Grabbing SLO System Operation OCT Ophthalmoscope OCT Principle of Operation Resolution Limits of OCT Light Detection Basic Layout of AO-OCT Ophthalmoscopes Optical Components Wavefront Sensing Imaging Light Source Field Size Impact of Speckle and Chromatic Aberrations Common Issues for all AO Imaging Systems Light Budget Human Factors Refraction Imaging Time Image Postprocessing Introduction Convolution Linear Deconvolution Nonlinear Deconvolution Uses of Deconvolution Summary 283

8 XI PART FOUR VISION CORRECTION APPLICATIONS Customized Vision Correction Devices 291 lan Cox 11.1 Contact Lenses Rigid or Soft Contact Lenses for Customized Correction? Design Considerations More Than Just Optics Measurement The Eye, the Lens, or the System? Customized Contact Lenses in a Disposable World Manufacturing Issues Can the Correct Surfaces Be Made? Who Will Benefit? Summary Intraocular Lenses Which Aberrations The Cornea, the Lens, or the Eye? Correcting Higher Order Aberrations Individual Versus Population Average Summary Customized Corneal Ablation 311 Scott M. MacRae 12.1 Introduction Basics of Laser Refractive Surgery Forms of Customization Functional Customization Anatomical Customization Optical Customization The Excimer Laser Treatment Biomechanics and Variable Ablation Rate Effect of the LASIK Flap Wavefront Technology and Higher Order Aberration Correction Clinical Results of Excimer Laser Ablation Summary From Wavefronts To Refractions 331 Larry N. Thibos 13.1 Basic Terminology Refractive Error and Refractive Correction Lens Prescriptions 332

9 13.2 Goal of Refraction Definition of the Far Point Refraction by Successive Elimination Using Depth of Focus to Expand the Range of Clear Vision Methods for Estimating the Monochromatic Refraction from an Aberration Map Refraction Based on Equivalent Quadratic Virtual Refraction Based on Maximizing Optical Quality Numerical Example Ocular Chromatic Aberration and the Polychromatic Refraction Polychromatic Wavefront Metrics Polychromatic Point Image Metrics Polychromatic Gräting Image Metrics Experimental Evaluation of Proposed Refraction Methods Monochromatic Predictions Polychromatic Predictions Conclusions 360 Visual Psychophysics With Adaptive Optics 363 Joseph L. Hardy, Peter B. Delahunt, and John S. Werner 14.1 Psychophysical Functions Contrast Sensitivity Functions Spectral Efficiency Functions Psychophysical Methods Threshold Signal Detection Theory Detection, Discrimination, and Identification Thresholds Procedures for Estimating a Threshold Psychometric Functions Selecting Stimulus Values Generating the Visual Stimulus General Issues Concerning Computer-Controlled Displays Types of Computer-Controlled Displays Accurate Stimulus Generation Display Characterization 388

10 XIII Maxwellian-View Optical Systems Other Display Options Conclusions 391 PART FIVE DESIGN EXAMPLES Rochester Adaptive Optics Ophthalmoscope 397 Heidi Hofer, Jason Porter, Geunyoung Yoon, Li Chen, Ben Singer, and David R. Williams 15.1 Introduction Optical Layout Wavefront Measurement and Correction Retinal Imaging: Light Delivery and Image Acquisition Visual Psychophysics Stimulus Display Control Algorithm Wavefront Correction Performance Residual RMS Errors, Wavefronts, and Point Spread Functions Temporal Performance: RMS Wavefront Error Improvement in Retinal Image Quality Improvement in Visual Performance Current System Limitations Conclusion Design of an Adaptive Optics Scanning Laser Ophthalmoscope 417 Krishnakumar Venkateswaran, Fernando Romero-Borja, and Austin Roorda Introduction Light Delivery Raster Scanning Adaptive Optics in the SLO Wavefront Sensing Wavefront Compensation Using the Deformable Mirror Mirror Control Algorithm Nonnulling Operation for Axial Sectioning in a Closed-Loop AO System Optical Layout for the AOSLO Image Acquisition

11 16.7 Software Interface for the AOSLO Calibration and Testing Defocus Calibration Linearity of the Detection Path Field Size Calibration AO Performance Results AO Compensation Axial Resolution of the Theoretically Modeled AOSLO and Experimental Results Imaging Results Hard Exudates and Microaneurysms in a Diabetic's Retina Blood Flow Measurements Solar Retinopathy Discussions on Improving Performance of the AOSLO Size of the Confocal Pinhole Pupil and Retinal Stabilization Improvements to Contrast 443 Indiana University AO-OCT System 447 Yan Zhang, Jungtae Rha, Ravi S. Jonnal, and Donald T. Miller 17.1 Introduction Description of the System Experimental Procedures Preparation of Subjects Collection of Retinal Images AO Performance Image Sharpening Temporal Power Spectra Power Rejection Curve of the Closed-Loop AO System Time Stamping of SHWS Measurements Extensive Logging Capabilities Improving Corrector Stability Example Results with AO Conventional Flood- Illuminated Imaging Example Results With AO Parallel SD-OCT Imaging Parallel SD-OCT Sensitivity and Axial Resolution AO Parallel SD-OCT Imaging Conclusion 474

12 xv 18 Design and Testing of A Liquid Crystal Adaptive Optics Phoropter 477 Abdul Avvwal and Scot Olivier 18.1 Introduction Wavefront Sensor Selection Wavefront Sensor: Shack-Hartmann Sensor Shack-Hartmann Noise Beacon Selection: Size and Power, SLD versus Laser Diode Wavefront Corrector Selection Wavefront Reconstruction and Control Closed-Loop Algorithm Centroid Calculation Software Interface AO Assembly, Integration, and Troubleshooting System Performance, Testing Procedures, and Calibration Nonlinear Characterization of the Spatial Light Modulator (SLM) Response Phase Wrapping Biased Operation of SLM Wavefront Sensor Verification Registration Closed-Loop Operation Results from Human Subjects Discussion Summary 508 APPENDIX A: OPTICAL SOCIETY OF AMERICA'S STANDARDS FOR REPORTING OPTICAL ABERRATIONS 511 GLOSSARY 529 SYMBOL TABLE 553 INDEX 565