Adaptive Optics for Vision Science

Jason Porter, PhD, is a post-doctoral research fellow at the University of Rochester's Center for Visual Science in the laboratory of Dr. David R. Williams. Julianna E. Lin, M.Eng, is a member of the Research and Technology Staff for the Xerox Innovation Group at the Wilson Center for Research and Technology in Webster, NY.  Hope Marcotte Queener, M.Sc, is an Application Developer at the University of Houston College of Optometry.Karen ThornAbdul Awwal, PhD, is a Research Scientist at the Lawrence Livermore National Laboratory.

• FOREWORD xviiACKNOWLEDGMENTS xxiCONTRIBUTORS xxiiiPART ONE INTRODUCTION 11 Development of Adaptive Optics in Vision Science and Ophthalmology 3David R. Williams and Jason Porter1.1 Brief History of Aberration Correction in the Human Eye 31.1.1 Vision Correction 31.1.2 Retinal Imaging 51.2 Applications of Ocular Adaptive Optics 91.2.1 Vision Correction 91.2.2 Retinal Imaging 11PART TWO WAVEFRONT MEASUREMENT AND CORRECTION 312 Aberration Structure of the Human Eye 33Pablo Artal, Juan M. Bueno, Antonio Guirao, and Pedro M. Prieto2.1 Introduction 332.2 Location of Monochromatic Aberrations Within the Eye 342.3 Temporal Properties of Aberrations: Accommodation and Aging 402.3.1 Effect of Accommodation on Aberrations and Their Correction 402.3.2 Aging and Aberrations 422.4 Chromatic Aberrations 432.4.1 Longitudinal Chromatic Aberration 442.4.2 Transverse Chromatic Aberration 452.4.3 Interaction Between Monochromatic and Chromatic Aberrations 452.5 Off-Axis Aberrations 462.5.1 Peripheral Refraction 472.5.2 Monochromatic and Chromatic Off-Axis Aberrations 482.5.3 Monochromatic Image Quality and Correction of Off-Axis Aberrations 512.6 Statistics of Aberrations in Normal Populations 522.7 Effects of Polarization and Scatter 532.7.1 Impact of Polarization on the Ocular Aberrations 532.7.2 Intraocular Scatter 553 Wavefront Sensing and Diagnostic Uses 63Geunyoung Yoon3.1 Wavefront Sensors for the Eye 633.1.1 Spatially Resolved Refractometer 653.1.2 Laser Ray Tracing 653.1.3 Shack–Hartmann Wavefront Sensor 663.2 Optimizing a Shack–Hartmann Wavefront Sensor 683.2.1 Number of Lenslets Versus Number of Zernike Coefficients 683.2.2 Trade-off Between Dynamic Range and Measurement Sensitivity 713.2.3 Focal Length of the Lenslet Array 733.2.4 Increasing the Dynamic Range of a Wavefront Sensor Without Losing Measurement Sensitivity 743.3 Calibration of a Wavefront Sensor 753.3.1 Reconstruction Algorithm 763.3.2 System Aberrations 773.4 Summary 794 Wavefront Correctors for Vision Science 83Nathan Doble and Donald T. Miller4.1 Introduction 834.2 Principal Components of an AO System 844.3 Wavefront Correctors 864.4 Wavefront Correctors Used in Vision Science 884.4.1 Macroscopic Discrete Actuator Deformable Mirrors 894.4.2 Liquid Crystal Spatial Light Modulators 904.4.3 Bimorph Mirrors 914.4.4 Microelectromechanical Systems 924.5 Performance Predictions for Various Types of Wavefront Correctors 954.5.1 Description of Two Large Populations 984.5.2 Required Corrector Stroke 994.5.3 Discrete Actuator Deformable Mirrors 1014.5.4 Piston-Only Segmented Mirrors 1064.5.5 Piston/Tip/Tilt Segmented Mirrors 1074.5.6 Membrane and Bimorph Mirrors 1094.6 Summary and Conclusion 1115 Control Algorithms 119Li Chen5.1 Introduction 1195.2 Configuration of Lenslets and Actuators 1195.3 Influence Function Measurement 1225.4 Spatial Control Command of the Wavefront Corrector 1245.4.1 Control Matrix for the Direct Slope Algorithm 1245.4.2 Modal Wavefront Correction 1275.4.3 Wave Aberration Generator 1275.5 Temporal Control Command of the Wavefront Corrector 1285.5.1 Open-Loop Control 1285.5.2 Closed-Loop Control 1295.5.3 Transfer Function of an Adaptive Optics System 1306 Adaptive Optics Software for Vision Research 139Ben Singer6.1 Introduction 1396.2 Image Acquisition 1406.2.1 Frame Rate 1406.2.2 Synchronization 1406.2.3 Pupil Imaging 1416.3 Measuring Wavefront Slope 1426.3.1 Setting Regions of Interest 1426.3.2 Issues Related to Image Coordinates 1436.3.3 Adjusting for Image Quality 1436.3.4 Measurement Pupils 1436.3.5 Preparing the Image 1436.3.6 Centroiding 1446.4 Aberration Recovery 1446.4.1 Principles 1446.4.2 Implementation 1456.4.3 Recording Aberration 1476.4.4 Displaying a Running History of RMS 1476.4.5 Displaying an Image of the Reconstructed Wavefront 1486.5 Correcting Aberrations 1496.5.1 Recording Influence Functions 1496.5.2 Applying Actuator Voltages 1506.6 Application-Dependent Considerations 1506.6.1 One-Shot Retinal Imaging 1506.6.2 Synchronizing to Display Stimuli 1506.6.3 Selective Correction 1516.7 Conclusion 1516.7.1 Making Programmers Happy 1516.7.2 Making Operators Happy 1516.7.3 Making Researchers Happy 1526.7.4 Making Subjects Happy 1526.7.5 Flexibility in the Middle 1537 Adaptive Optics System Assembly and Integration 155Brian J. Bauman and Stephen K. Eisenbies7.1 Introduction 1557.2 First-Order Optics of the AO System 1567.3 Optical Alignment 1577.3.1 Understanding Penalties for Misalignments 1587.3.2 Optomechanics 1597.3.3 Common Alignment Practices 1637.3.4 Sample Procedure for Offl ine Alignment 1707.4 AO System Integration 1747.4.1 Overview 1747.4.2 Measure the Wavefront Error of Optical Components 1757.4.3 Qualify the DM 1757.4.4 Qualify the Wavefront Sensor 1777.4.5 Check Wavefront Reconstruction 1807.4.6 Assemble the AO System 1817.4.7 Boresight FOVs 1827.4.8 Perform DM-to-WS Registration 1837.4.9 Measure the Slope Infl uence Matrix and Generate Control Matrices 1847.4.10 Close the Loop and Check the System Gain 1847.4.11 Calibrate the Reference Centroids 1858 System Performance Characterization 189Marcos A. van Dam8.1 Introduction 1898.2 Strehl Ratio 1898.3 Calibration Error 1918.4 Fitting Error 1928.5 Measurement and Bandwidth Error 1948.5.1 Modeling the Dynamic Behavior of the AO System 1948.5.2 Computing Temporal Power Spectra from the Diagnostics 1968.5.3 Measurement Noise Errors 1988.5.4 Bandwidth Error 1998.5.5 Discussion 2008.6 Addition of Wavefront Error Terms 200PART THREE RETINAL IMAGING APPLICATIONS 2039 Fundamental Properties of the Retina 205Ann E. Elsner9.1 Shape of the Retina 2069.2 Two Blood Supplies 2099.3 Layers of the Fundus 2109.4 Spectra 2189.5 Light Scattering 2209.6 Polarization 2259.7 Contrast from Directly Backscattered or Multiply Scattered Light 2289.8 Summary 23010 Strategies for High-Resolution Retinal Imaging 235Austin Roorda, Donald T. Miller, and Julian Christou10.1 Introduction 23510.2 Conventional Imaging 23610.2.1 Resolution Limits of Conventional Imaging Systems 23710.2.2 Basic System Design 23710.2.3 Optical Components 23910.2.4 Wavefront Sensing 24010.2.5 Imaging Light Source 24210.2.6 Field Size 24410.2.7 Science Camera 24610.2.8 System Operation 24610.3 Scanning Laser Imaging 24710.3.1 Resolution Limits of Confocal Scanning Laser Imaging Systems 24910.3.2 Basic Layout of an AOSLO 24910.3.3 Light Path 24910.3.4 Light Delivery 25110.3.5 Wavefront Sensing and Compensation 25210.3.6 Raster Scanning 25310.3.7 Light Detection 25410.3.8 Frame Grabbing 25510.3.9 SLO System Operation 25510.4 OCT Ophthalmoscope 25610.4.1 OCT Principle of Operation 25710.4.2 Resolution Limits of OCT 25910.4.3 Light Detection 26210.4.4 Basic Layout of AO-OCT Ophthalmoscopes 26410.4.5 Optical Components 26610.4.6 Wavefront Sensing 26610.4.7 Imaging Light Source 26710.4.8 Field Size 26710.4.9 Impact of Speckle and Chromatic Aberrations 26810.5 Common Issues for all AO Imaging Systems 27110.5.1 Light Budget 27110.5.2 Human Factors 27210.5.3 Refraction 27210.5.4 Imaging Time 27610.6 Image Postprocessing 27610.6.1 Introduction 27610.6.2 Convolution 27610.6.3 Linear Deconvolution 27810.6.4 Nonlinear Deconvolution 27910.6.5 Uses of Deconvolution 28310.6.6 Summary 283PART FOUR VISION CORRECTION APPLICATIONS 28911 Customized Vision Correction Devices 291Ian Cox11.1 Contact Lenses 29111.1.1 Rigid or Soft Contact Lenses for Customized Correction? 29311.1.2 Design Considerations—More Than Just Optics 29511.1.3 Measurement—The Eye, the Lens, or the System? 29711.1.4 Customized Contact Lenses in a Disposable World 29811.1.5 Manufacturing Issues—Can the Correct Surfaces Be Made? 30011.1.6 Who Will Benefit? 30111.1.7 Summary 30411.2 Intraocular Lenses 30411.2.1 Which Aberrations—The Cornea, the Lens, or the Eye? 30511.2.2 Correcting Higher Order Aberrations—Individual Versus Population Average 30611.2.3 Summary 30812 Customized Corneal Ablation 311Scott M. MacRae12.1 Introduction 31112.2 Basics of Laser Refractive Surgery 31212.3 Forms of Customization 31712.3.1 Functional Customization 31712.3.2 Anatomical Customization 31912.3.3 Optical Customization 32012.4 The Excimer Laser Treatment 32112.5 Biomechanics and Variable Ablation Rate 32212.6 Effect of the LASIK Flap 32412.7 Wavefront Technology and Higher Order Aberration Correction 32512.8 Clinical Results of Excimer Laser Ablation 32512.9 Summary 32613 From Wavefronts To Refractions 331Larry N. Thibos13.1 Basic Terminology 33113.1.1 Refractive Error and Refractive Correction 33113.1.2 Lens Prescriptions 33213.2 Goal of Refraction 33413.2.1 Definition of the Far Point 33413.2.2 Refraction by Successive Elimination 33513.2.3 Using Depth of Focus to Expand the Range of Clear Vision 33613.3 Methods for Estimating the Monochromatic Refraction from an Aberration Map 33713.3.1 Refraction Based on Equivalent Quadratic 33913.3.2 Virtual Refraction Based on Maximizing Optical Quality 33913.3.3 Numerical Example 35313.4 Ocular Chromatic Aberration and the Polychromatic Refraction 35413.4.1 Polychromatic Wavefront Metrics 35613.4.2 Polychromatic Point Image Metrics 35713.4.3 Polychromatic Grating Image Metrics 35713.5 Experimental Evaluation of Proposed Refraction Methods 35813.5.1 Monochromatic Predictions 35813.5.2 Polychromatic Predictions 35913.5.3 Conclusions 36014 Visual Psychophysics With Adaptive Optics 363Joseph L. Hardy, Peter B. Delahunt, and John S. Werner14.1 Psychophysical Functions 36414.1.1 Contrast Sensitivity Functions 36414.1.2 Spectral Efficiency Functions 36814.2 Psychophysical Methods 37014.2.1 Threshold 37014.2.2 Signal Detection Theory 37114.2.3 Detection, Discrimination, and Identification Thresholds 37414.2.4 Procedures for Estimating a Threshold 37514.2.5 Psychometric Functions 37714.2.6 Selecting Stimulus Values 37814.3 Generating the Visual Stimulus 38014.3.1 General Issues Concerning Computer-Controlled Displays 38114.3.2 Types of Computer-Controlled Displays 38414.3.3 Accurate Stimulus Generation 38614.3.4 Display Characterization 38814.3.5 Maxwellian-View Optical Systems 39014.3.6 Other Display Options 39014.4 Conclusions 391PART FIVE DESIGN EXAMPLES 39515 Rochester Adaptive Optics Ophthalmoscope 397Heidi Hofer, Jason Porter, Geunyoung Yoon, Li Chen, Ben Singer, and David R. Williams15.1 Introduction 39715.2 Optical Layout 39815.2.1 Wavefront Measurement and Correction 39815.2.2 Retinal Imaging: Light Delivery and Image Acquisition 40315.2.3 Visual Psychophysics Stimulus Display 40415.3 Control Algorithm 40515.4 Wavefront Correction Performance 40615.4.1 Residual RMS Errors, Wavefronts, and Point Spread Functions 40615.4.2 Temporal Performance: RMS Wavefront Error 40715.5 Improvement in Retinal Image Quality 40915.6 Improvement in Visual Performance 41015.7 Current System Limitations 41215.8 Conclusion 41416 Design of an Adaptive Optics Scanning Laser Ophthalmoscope 417Krishnakumar Venkateswaran, Fernando Romero-Borja, and Austin Roorda16.1 Introduction 41716.2 Light Delivery 41916.3 Raster Scanning 41916.4 Adaptive Optics in the SLO 42016.4.1 Wavefront Sensing 42016.4.2 Wavefront Compensation Using the Deformable Mirror 42116.4.3 Mirror Control Algorithm 42116.4.4 Nonnulling Operation for Axial Sectioning in a Closed-Loop AO System 42316.5 Optical Layout for the AOSLO 42516.6 Image Acquisition 42616.7 Software Interface for the AOSLO 42916.8 Calibration and Testing 43116.8.1 Defocus Calibration 43116.8.2 Linearity of the Detection Path 43216.8.3 Field Size Calibration 43216.9 AO Performance Results 43216.9.1 AO Compensation 43216.9.2 Axial Resolution of the Theoretically Modeled AOSLO and Experimental Results 43416.10 Imaging Results 43816.10.1 Hard Exudates and Microaneurysms in a Diabetic’s Retina 43816.10.2 Blood Flow Measurements 43916.10.3 Solar Retinopathy 44016.11 Discussions on Improving Performance of the AOSLO 44116.11.1 Size of the Confocal Pinhole 44116.11.2 Pupil and Retinal Stabilization 44316.11.3 Improvements to Contrast 44317 Indiana University AO-OCT System 447Yan Zhang, Jungtae Rha, Ravi S. Jonnal, and Donald T. Miller17.1 Introduction 44717.2 Description of the System 44817.3 Experimental Procedures 45317.3.1 Preparation of Subjects 45317.3.2 Collection of Retinal Images 45417.4 AO Performance 45517.4.1 Image Sharpening 45717.4.2 Temporal Power Spectra 45817.4.3 Power Rejection Curve of the Closed-Loop AO System 45917.4.4 Time Stamping of SHWS Measurements 46017.4.5 Extensive Logging Capabilities 46117.4.6 Improving Corrector Stability 46117.5 Example Results with AO Conventional Flood-Illuminated Imaging 46117.6 Example Results With AO Parallel SD-OCT Imaging 46317.6.1 Parallel SD-OCT Sensitivity and Axial Resolution 46317.6.2 AO Parallel SD-OCT Imaging 46617.7 Conclusion 47418 Design and Testing of A Liquid Crystal Adaptive Optics Phoropter 477Abdul Awwal and Scot Olivier18.1 Introduction 47718.2 Wavefront Sensor Selection 47818.2.1 Wavefront Sensor: Shack–Hartmann Sensor 47818.2.2 Shack–Hartmann Noise 48318.3 Beacon Selection: Size and Power, SLD versus Laser Diode 48418.4 Wavefront Corrector Selection 48518.5 Wavefront Reconstruction and Control 48618.5.1 Closed-Loop Algorithm 48718.5.2 Centroid Calculation 48818.6 Software Interface 48918.7 AO Assembly, Integration, and Troubleshooting 49118.8 System Performance, Testing Procedures, and Calibration 49218.8.1 Nonlinear Characterization of the Spatial Light Modulator (SLM) Response 49318.8.2 Phase Wrapping 49318.8.3 Biased Operation of SLM 49518.8.4 Wavefront Sensor Verification 49518.8.5 Registration 49618.8.6 Closed-Loop Operation 49918.9 Results from Human Subjects 50218.10 Discussion 50618.11 Summary 508APPENDIX A: OPTICAL SOCIETY OF AMERICA’S STANDARDS FOR REPORTING OPTICAL ABERRATIONS 511GLOSSARY 529SYMBOL TABLE 553INDEX 565