- •Visual Prosthetics
- •Preface
- •Acknowledgments
- •Contents
- •Contributors
- •1.1 The Visual System as an Engineering Compromise
- •1.2 An Overview of Human Visual System Architecture
- •1.2.1 Architecture and Basic Function of the Eye
- •1.2.2 Layout of the Retino-Cortical Pathway
- •1.2.3 Layout of the Subcortical Pathways
- •1.3 An Overview of Human Visual Function
- •1.3.1 Roles of Central (Foveal) Vision
- •1.3.2 Roles of Peripheral Vision
- •1.3.3 Roles of Dark-Adapted Vision
- •1.3.4 A Few Remarks Regarding Visual Development
- •1.4 Prospects for Prosthetic Vision Restoration
- •References
- •2.1 Introduction
- •2.2 Retina
- •2.2.1 Anatomy
- •2.2.2 Physiology and Receptive Fields
- •2.4.1 Anatomy
- •2.4.2 Physiology and Receptive Fields
- •2.6 The Role of Spatiotemporal Edges in Early Vision
- •2.7 The Role of Corners in Early Vision
- •2.7.1 Overview
- •2.8 Effects of Fixational Eye Movements in Early Visual Physiology and Perception
- •2.8.1 Overview
- •2.8.2 Neural Adaptation and Visual Fading
- •2.8.3 Microsaccades in Visual Physiology and Perception
- •References
- •3.1 Introduction
- •3.2 Background
- •3.3 Retinal Disease and Its Diversity
- •3.4 Retinal Remodeling
- •3.5 Retinal Circuitry
- •3.6 Retinal Circuitry Revision
- •3.7 Implications for Bionic Rescue
- •3.8 Implications for Biological Rescue
- •3.9 Final Remarks
- •References
- •4.1 Introduction
- •4.4 What Are the Limits to This Cortical Plasticity?
- •4.5 Possible Mechanisms Behind Brain Plasticity
- •4.6 Modulation of Brain Plasticity: Recent Developments
- •4.7 Neuroplasticity and Other Neuroprostheses Efforts
- •4.8 A Look at What Is Ahead
- •References
- •5.1 Introduction
- •5.2 Vision Changes Experienced by RP Patients
- •5.2.1 Overview
- •5.2.2 Visual Field Loss in RP
- •5.2.3 Changes in Color Vision and Glare Sensitivity in RP
- •5.2.4 Vision Fluctuations in RP
- •5.3 Visual Changes in Patients with Advanced Macular Degeneration
- •5.3.1 Changes Due to Wet AMD or Choroidal Neovascularization
- •5.3.2 Changes Due to Dry AMD or Geographic Atrophy
- •5.4 Charles Bonnet Syndrome
- •5.4.1 Overview
- •5.4.2 Complexity of Visual Hallucinations in CBS
- •5.4.3 Predictors and Alleviating Factors for CBS
- •5.5 Filling-In Phenomena (Perceptual Completion)
- •5.6 Remapping of Primary Visual Cortex in Patients with Central Scotomas from Macular Disease
- •5.7 The Preferred Retinal Locus for Fixation
- •5.8 Photopsias
- •5.8.1 Photopsias in RP
- •5.8.2 Photopsias in AMD and Other Ocular Diseases
- •5.9 Concluding Remarks
- •References
- •6.1 Introduction
- •6.2 Electrode–Electrolyte Interface
- •6.3 Electrode Material
- •6.3.1 Electrode Characterization
- •6.4 Overview of Electrode Materials for Neural Stimulation
- •6.5 Overview of Extracellular Stimulation
- •6.6 Safe Stimulation of Tissue
- •6.6.1 Mechanisms of Neural Injury
- •6.6.2 Parameters for Safe Stimulation
- •6.6.3 Stimulation Induced Injury in the Retina
- •References
- •7.1 Introduction
- •7.2 Power and Data Transmission
- •7.2.1 Wireline Connection
- •7.2.2 Inductive Coils
- •7.2.3 Serial Optical Telemetry
- •7.2.4 Photodiode Array-Based Prostheses
- •7.2.5 Thermal Safety Considerations
- •7.2.6 Conclusions: Comparing the Different Approaches
- •7.3 Tissue Response to a Subretinal Implant
- •7.3.1 Flat Implants
- •7.3.2 Chamber Implants
- •7.3.3 Pillar Arrays
- •7.4 Damage to Retinal Tissue from Electrical Stimulation
- •7.4.1 Effect of Pulse Duration
- •7.4.2 Electrode Size
- •7.5 Concluding Remarks
- •References
- •8.1 Introduction
- •8.2 Quasistatic Numerical Methods: The Admittance Method
- •8.2.1 Layered Retinal Model
- •8.2.2 Equivalent Electric Circuit
- •8.3 Three-Dimensional Activation Function Calculation
- •8.4 Safety of Implant
- •8.5 Conclusion
- •References
- •9.1 Pathophysiology of Retinal Degeneration
- •9.2.1 Outer Plexiform Layer
- •9.2.2 Inner Plexiform Layer
- •9.2.2.1 Bipolar Cell Excitation of Retinal Ganglion Cells
- •9.2.2.2 Amacrine Cell Modulation of Signal Processing
- •9.2.2.3 Inhibitory Transmitters
- •9.2.2.4 Acetylcholine and Dopamine
- •9.2.2.5 Neuropeptides
- •9.2.2.6 Putative neurotransmitters for retinal prosthesis
- •9.3 Neurophysiological Changes in Retinal Degeneration
- •9.4 Rationale for a Neurotransmitter-Based Retinal Prosthesis
- •9.4.1 Limitations of Electrical Stimulation
- •9.5 Technical Considerations and Design Approaches
- •9.5.1 Operating Principles for a Neurotransmitter-Based Retinal Prosthesis
- •9.5.2 Establishing a Retinal Prosthesis/Synaptic Interface
- •9.5.2.1 The Proximity Requirement
- •9.5.2.2 Convective Delivery of Neurotransmitters Via Microfluidics
- •9.5.2.3 Functionalized Surfaces for Neurotransmitter Stimulation
- •9.5.2.4 Synaptic Requirements for l-Glutamate Mediated Neuronal Stimulation
- •9.6 Summary
- •References
- •10.1 Introduction
- •10.2 Pioneering Experiments
- •10.2.1 Stimulation with No Chromophores
- •10.2.2 Azo Chromophores
- •10.3 Current Research
- •10.3.1 Caged Neurotransmitters
- •10.3.2 Pore Blocker and Photoisomerization
- •10.3.3 The Channelrhodopsins
- •10.3.4 Melanopsin
- •10.4 Synthetic Chromophores and Artificial Sight
- •References
- •11.1 Background
- •11.2 Physical Structure of Intracortical Electrodes
- •11.3 Charge Injection Using Intracortical Electrodes
- •11.3.1 The Intracortical Electrode as a Transducer
- •11.3.2 Charge Injection Limits
- •11.4 Intracortical Electrode Coatings
- •11.5 Characterization of Intracortical Electrodes
- •11.5.1 Cyclic Voltammetry
- •11.5.2 Electrode Stimulation Voltage Waveforms
- •11.5.3 Non-ideal Access Resistance Behavior
- •11.5.4 Non-linear Electrode Polarization
- •11.5.5 Determining Electrode Safety
- •11.6 Contrasts of In Vitro and In Vivo Behavior
- •11.7 Alternative Coatings for Improving Intracortical Electrodes
- •11.7.1 SIROF
- •11.7.2 PEDOT
- •11.7.3 Carbon Nanotube Coatings
- •11.8 Conclusion
- •References
- •12.1 Introduction
- •12.2 Responses of RGCs to Electrical Stimulation in Normal Retina
- •12.2.1 Epiretinal Stimulation
- •12.2.1.1 Target of Stimulation
- •12.2.1.2 The Site of Spike Initiation in RGCs
- •12.2.1.3 Threshold vs. Stimulating Electrode Diameter
- •12.2.1.4 Spatial Extent of Activation
- •12.2.1.5 Selective Activation
- •12.2.1.6 Temporal Response Properties
- •12.2.2 Subretinal Stimulation
- •12.2.2.1 Target of Stimulation
- •12.2.2.2 Threshold vs. Polarity of Stimulation Pulse
- •12.2.2.3 Spatial Extent of Activation
- •12.2.2.4 Temporal Response Properties
- •12.2.2.5 Dynamics of the Retinal Response
- •12.4 Responses of RGCs to Electrical Stimulation in Degenerate Retina
- •12.4.1 Epiretinal Stimulation
- •12.4.2 Subretinal Stimulation
- •12.4.2.1 Response Properties of RGCs
- •12.4.2.2 Activation Thresholds of RGCs
- •12.5 Cortical Responses to Retinal Stimulation
- •12.5.1 Spatial Properties Revealed by Cortical Measurements
- •12.5.2 Local Field Potentials
- •12.5.3 Elicited Responses Are Focal
- •12.5.4 Cortical Measurements Reveal Electrode Interactions
- •12.5.5 Temporal Responsiveness in Cortex
- •12.6 Suggestions for Future Studies
- •References
- •13.1 Introduction
- •13.2 General Considerations for Acute Retinal Stimulation Experiments
- •13.3 Surgical Technique
- •13.4 Threshold Measurements
- •13.5 Spatial Resolution and Pattern Perception
- •13.6 Temporal Resolution
- •13.7 Subretinal Versus Epiretinal Stimulation
- •13.8 Less Invasive Stimulation Procedures
- •13.9 Conclusions and Outlook
- •References
- •14.1 Introduction
- •14.2 Overview of Chronic Retinal Implant Technologies
- •14.2.1 The Retinal Implant AG Microphotodiode Prosthesis
- •14.2.2 The Intelligent Retinal Implant System
- •14.2.3 Second Sight Medical Products, Inc. A16 System
- •14.3 Thresholds on Individual Electrodes
- •14.3.1 Single Pulse Thresholds Using the SSMP System
- •14.3.2 Pulse Train Integration and Temporal Sensitivity
- •14.4 Suprathreshold Brightness
- •14.4.1 Brightness Using the Retinal Implant AG System
- •14.4.2 Brightness Using the Intelligent Medical Implant System
- •14.4.3 Brightness Using the SSMP A16 System
- •14.5 Spatial Vision
- •14.5.1 Spatial Vision with the Retinal Implant AG System
- •14.5.2 Spatial Vision with the Intelligent Medical Implant System
- •14.5.3 Spatial Vision with the SSMP A16 System
- •14.6 Models to Guide Electrical Stimulation Protocols
- •14.7 Conclusions
- •References
- •15.1 Background
- •15.2 Cortical Surface Stimulation
- •15.3 Intracortical Microstimulation
- •15.4 Optic Nerve Stimulation
- •15.5 What Is Known and What Needs to Be Done
- •15.6 Current Research Efforts
- •15.6.1 Optic Nerve Stimulation
- •15.6.2 Cortical Surface Stimulation
- •15.6.3 Intracortical Stimulation of Visual Cortex
- •15.6.4 CORTIVIS Program
- •15.6.5 Lateral Geniculate Stimulation
- •15.7 Microelectrode Arrays and Stimulation Hardware
- •15.7.1 Miniature Cameras
- •15.7.2 Animal Models
- •15.7.3 Image Processing and Phosphene Mapping
- •15.8 Conclusion
- •References
- •16.1 Introduction
- •16.2 Simulation Techniques and Basic Parameters
- •16.2.1 Gaze Tracking and Image Stabilization
- •16.2.2 Filter Engine Parameters
- •16.2.2.1 Raster Spatial Properties
- •16.2.2.2 Dot Spatial Properties
- •16.2.2.3 Temporal Properties
- •16.2.2.4 Dynamic Background Noise
- •16.2.2.5 Input Filtering/Windowing, Image Enhancement
- •16.3 Optotype Resolution and Reading
- •16.3.1 Visual Acuity
- •16.3.2 Reading
- •16.4 Face and Object Recognition
- •16.5 Visually Guided Behavior
- •16.5.1 Hand–Eye Coordination
- •16.5.2 Wayfinding
- •16.6 Visual Tracking
- •16.7 Computational Simulations
- •16.8 Conclusion
- •References
- •17.1 Introduction
- •17.2 Situating Image Analysis
- •17.3 The Experimental Framework
- •17.4 Tracking a Low-Resolution Target
- •17.5 Discussion
- •17.6 Conclusion
- •References
- •18.1 Introduction
- •18.2 Representation of Visual Space on the Visual Cortex
- •18.3 Cortical Stimulation Studies
- •18.4 Variability in Occipital Cortex
- •18.5 Phosphene Map Estimation
- •18.6 Psychophysical Studies with the Estimated Maps
- •References
- •19.1 Importance of Mapping
- •19.3 The Computer Era: Refining the Pointing Method of Phosphene Mapping
- •19.4 Verbal Mapping
- •19.5 Mapping Studies Using Subject Drawings
- •19.6 Recent Simulation Studies Using Phosphene Mapping
- •19.6.1 Tactile Simulations at Shanghai Jiao Tong University
- •19.6.2 Simulations in Our Laboratory
- •19.7 Concluding Remarks on Phosphene Mapping Techniques
- •References
- •20.1 Introduction
- •20.2 Principles for Assessment of Prosthetic Vision
- •20.2.1 Experimental Design
- •20.2.2 The Importance of Pre-operative Testing
- •20.2.3 Post-operative Assessment
- •20.2.4.1 Potential Approaches
- •20.2.4.2 Avoidance of Bias
- •20.2.4.3 Criteria for Sound Testing
- •20.2.4.4 Forced Choice Procedures
- •20.2.4.5 Response Time
- •20.2.4.6 Task (Perceptual) Learning
- •20.2.4.7 Establishing Criteria for Meaningful Change
- •20.2.4.8 Light Level
- •20.3 Vision Assessment in Prosthesis Recipients: Overview
- •20.3.1 Visual Function Assessment: Overview
- •20.3.2 Visual Performance Assessment: Overview
- •20.3.2.1 Measured Visual Performance
- •20.3.2.2 Self-Reported Visual Performance
- •20.4 Visual Function Assessment
- •20.4.1 Candidate Measures
- •20.4.1.1 Contrast Sensitivity (Contrast Detection)
- •20.4.1.2 Contrast Discrimination
- •20.4.1.3 Motion Perception
- •20.4.1.4 Depth Perception
- •20.4.2 Tests Used in Prosthesis Trials
- •20.4.3 Tests that Have Been Designed for Use with Prostheses
- •20.4.4 Vision Tests for Very Low Vision
- •20.5 Visual Performance Assessment
- •20.5.1 Measured Performance
- •20.5.2 Self-Reported Performance (Questionnaires)
- •20.6 Summary
- •References
- •21.1 Concepts of Functional Vision and Rehabilitation
- •21.1.1 Application to Orientation and Mobility
- •21.1.2 Application for Activities of Daily Living
- •21.1.3 Patient Lifestyle and Expectations
- •21.1.4 Congenital and Adventitious Vision Loss
- •21.2 Evaluation and Intervention with Prosthetic Vision
- •21.2.1 Evaluation
- •21.2.2 Intervention
- •21.3 Measuring Functional Outcomes
- •21.4 The Future
- •References
- •Author Index
- •Subject Index
Acknowledgments
This book reflects a group effort. Each contributor embraced the concept of a book that would span many disciplines, and reaching a consensus about what should be covered, and by which authors, proved surprisingly easy. I thank the authors for making time in their busy schedules to share their knowledge and create this overview.
I appreciate the encouragement of my colleagues at the Lions Vision Research and Rehabilitation Center of the Wilmer Eye Institute at Johns Hopkins, who encouraged me to take on the challenge of creating this book and who helped in large and small ways to bring it to completion. I am deeply grateful to Maryam Khan, M.D., who helped me turn a stack of diverse manuscripts into polished chapters that not only met the publisher’s technical standards but are a pleasure to read. But most of all, I am grateful to the study participants who give meaning to our research, and who are an ongoing source of inspiration. This book is dedicated to them.
Baltimore, MD |
Gislin Dagnelie |
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Contents
Preface.............................................................................................................. |
v |
Part I Structure and Function of the Visual System |
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1 The Human Visual System: An Engineering Perspective.................... |
3 |
Gislin Dagnelie |
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2 Vision’s First Steps: Anatomy, Physiology, and Perception in the Retina, Lateral Geniculate Nucleus, and Early
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Visual Cortical Areas.............................................................................. |
23 |
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Xoana G. Troncoso, Stephen L. Macknik, and Susana Martinez-Conde |
|
3 |
Retinal Remodeling and Visual Prosthetics.......................................... |
59 |
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Bryan W. Jones, Robert E. Marc, and Carl B. Watt |
|
4 |
Cortical Plasticity and Reorganization in Severe Vision Loss............. |
77 |
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Eduardo Fernández and Lotfi B. Merabet |
|
5 |
Visual Perceptual Effects of Long-Standing Vision Loss..................... |
93 |
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Ava K. Bittner and Janet S. Sunness |
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Part II Neural Stimulation of the Visual System |
|
|
6 |
Structures, Materials, and Processes |
|
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at the Electrode-to-Tissue Interface....................................................... |
113 |
|
Aditi Ray and James D. Weiland |
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7 Delivery of Information and Power to the Implant, |
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|
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Integration of the Electrode Array with the Retina, |
|
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and Safety of Chronic Stimulation......................................................... |
137 |
|
James Loudin, Alexander Butterwick, Philip Huie, and Daniel Palanker |
|
xi
xii |
|
Contents |
8 Retinal Cell Excitation Modeling........................................................... |
159 |
|
|
Carlos J. Cela and Gianluca Lazzi |
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9 Neurotransmitter Stimulation for Retinal Prosthesis: |
|
|
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The Artificial Synapse Chip.................................................................... |
173 |
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Raymond Iezzi and Paul G. Finlayson |
|
10 |
Synthetic Chromophores and Neural Stimulation |
|
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of the Visual System................................................................................. |
193 |
|
Elias Greenbaum and Barbara R. Evans |
|
11 |
Biophysics/ Engineering of Cortical Electrodes.................................... |
207 |
|
Philip R. Troyk |
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Part III Prosthetic Visual Function: Acute and Chronic |
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|
12 |
The Response of Retinal Neurons to Electrical Stimulation: |
|
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A Summary of In Vitro and In Vivo Animal Studies........................... |
229 |
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Shelley I. Fried and Ralph J. Jensen |
|
13 |
Findings from Acute Retinal Stimulation in Blind Patients................ |
259 |
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Peter Walter and Gernot Roessler |
|
14 |
The Perceptual Effects of Chronic Retinal Stimulation....................... |
271 |
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Alan Horsager and Ione Fine |
|
15 |
Findings from Chronic Optic Nerve and Cortical Stimulation........... |
301 |
|
Edward M. Schmidt |
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Part IV Towards Prosthetic Vision: Simulation, |
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|
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Assessment, Rehabilitation |
|
16 |
Simulations of Prosthetic Vision............................................................. |
319 |
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Michael P. Barry and Gislin Dagnelie |
|
17 |
Image Analysis, Information Theory and Prosthetic Vision............... |
343 |
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Luke E. Hallum and Nigel H. Lovell |
|
18 |
Simulations of Cortical Prosthetic Vision.............................................. |
355 |
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Nishant R. Srivastava |
|
19 |
Phosphene Mapping Techniques for Visual Prostheses....................... |
367 |
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H. Christiaan Stronks and Gislin Dagnelie |
|
20 |
Prosthetic Vision Assessment.................................................................. |
385 |
|
Marilyn E. Schneck and Gislin Dagnelie |
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Contents |
xiii |
21 Activities of Daily Living and Rehabilitation |
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with Prosthetic Vision.............................................................................. |
413 |
Duane R. Geruschat and James Deremeik |
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Author Index.................................................................................................... |
425 |
Subject Index................................................................................................... |
447 |
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