Ординатура / Офтальмология / Английские материалы / Artificial Sight Basic Research, Biomedical Engineering, and Clinical Advances_Humayun, Weiland, Chader_2007

2-amino-4-phosphonobutyrate, 376

2D models, 298

2D retinal image, projection of into a 3D world, 59

Acrylic, 1, 5

Activities of daily living and orientation, testing of, 105–108

Admittance method, 295 Adverse effects, 125

Age-related macular degeneration, 14–15, 32, 129, 170, 209, 223, 255, 280, 334, 347

disciform, 15, 17 dry, 14, 15 incidence of, 14 neovascular, 14 treatments for, 15 wet, 14

research on, 15 Agonists, 365, 374–378

definition of, 374–375 Algorithms, 115, 132, 198 image-processing, 132

Aluminum, 152, 159 Amacrine cells, 114 , 353, 365 Amblyopsis, 102–103

Ames’ medium, 214–215 Ampere’s Law, 281 Anatomy of the eye, 2–9 Anecortave acetate, 15 Animal experiments, 189–197

Animal models, 33–39, 93, 367 Animals, experimental

cats, 37, 38–39, 212, 213, 316, 317, 318, 319 chickens, 267–270

dogs, 10, 20, 60 frogs, 161, 167

guinea pigs, 219, 334, 335, 338, 339, 342 macaques, 48–49, 335

mice, 364 mini pigs, 119

monkeys, 48–49, 55, 57, 309, 310, 311, 319, 333–335, 338, 339

pigs, 367

rabbits, 36–38, 189, 190, 197, 267–270, 325–331, 348, 367

rats, 34, 39, 267–270, 334, 338–339, 342, 361, 367, 370

Anodic reactions, 232–234 Anterior chamber, 4, 5, 9 Antiangiogenic drugs, 15 Aqueous humor, 4

Artifact subtraction, 337–340, 343 Artificial sight, 219, 343 Artificial vision devices, 91

resolution and acuity of, 98 Aspartate, 365, 375, 376, 378

Attachment of an array to the retina, 20–23 Auditory cortex

changes in/changes of blind subjects, 53 cross-modal connections to, 56 cross-modal responses in, 56 deterioration of in deaf individuals, 61–62 recruitment of, 56

Auditory deprivation, 48, 54, 561

Auditory development, critical period for, 61 Average evoked response, 321

Axons, 316

optic nerve, 355

retinal ganglion cell, 34

BaGA test, 99, 102–103, 104–105 technical setup for, 98–100

BaLM test, 97, 98, 99, 100, 103, 105 technical setup for, 97, 98

Basic fibroblast growth factor, 40, 42 Basic grating acuity test, 99, 103

technical setup for, 103

Basic light and motion test, 97, 98 technical setup for, 97

Batteries, 116, 121, 172

Behavioral symptoms, measurement of, 108 Bidirectional communication, 172, 175 Binarization circuit, 158

Binary morphological operations, 158

382 Index

Bioadhesives, 21

Biocompatibility, 119, 159, 206, 211, 218, 223, 229, 244, 280, 369

Bioelectrical signals, conduction of, 194, 196 Bio-heat equation, 284, 285

formulation of, 284–287 Biological environment, protection

against, 159

Biological tissue, electrical stimulation of, 252

Biphasic current controllers, 172, 182–184 Biphasic current pulses, 161, 167, 202, 203,

230, 247

Biphasic current waveforms, 170, 182 Biphasic output, 154

Biphasic pulses, 38, 216, 217, 218, 219, 220, 223, 233, 235, 308, 349

charge-balanced, 235, 309 current, 161, 167, 202, 203, 247,

251–252, 333

minimization of pH changes by, 235 square-wave, 370–371

Biphasic stimulation, 140

Biphasic voltage generator, pulsed, 274 Biphasic waveforms, 171, 181, 184 Bipolar cells, 6, 257, 280, 365, 374, 376

retinal, 259

Blindness, early and late, 51 Blood circulation, 289

Blood perfusion, 285, 287, 289 Blurring, 157, 158

Braille reading, 54–55, 64 Brain

direct stimulation of, 353, 372 plasticity of, 47

posterior (occipital) pole of, 308 Brain-derived neurotrophic factor, 40, 42 Brief symptom inventory (BSI), 108 Brightness

perception of, 124–125 testing of, 100

Broadcast architectures, 166 Brodmann’s areas, 56, 57 Buffering, 232

Buffers, data, 176

Cameras, 258, 280

charge coupled device, 73 CMOS, 197

implantable, 188 digital, 111, 112, 129, 132 micro

evaluation of, 204–205 implantable, 203–206

video, 270–271 Capacitance, 153 Capacitive charge flow, 252

Capacitors, storage, 142–143 Carbon black, 264 Cataracts, 5, 50

removal of, learning deficit after, 50 Cataract surgery, 1, 5, 22

diagram of, 5

Cathodic reactions, 232–233 CCD array, 273

Cell membrane, depolarization of, 261 Cells

polarization of, 259 recruitment of, 372

Cell stimulation, voltage and current required for, 259–261

Cellular translocation, 17

Central nervous system, 212, 219, 319, 358 Cerebral cortex

cat, 313, 317 microstimulation of, 307–321

Charge, 38

Charge capacity, electrode material, 117 Charge coupled device, 73, 197

Charge coupled device array, 273

Charge densities, 37–38, 194, 221, 244, 264, 331, 338, 353

electrode–electrolyte interface, 211 levels of, 121

low, 342

reducing the size of stimulating electrodes on, effects of, 353

stimulus, 312–314 very high, 342

Charge density burden, 212

Charge density thresholds, 18–19, 37–38, 215–216, 264, 333–334

Charge injection capability, 251–253 Charge injection, neuralprosthesis, 229 Charge per phase, stimulus, 312–314 Charge stimulation thresholds, 334 Charge storage, 213

Charge transfer resistance, 262 Checkerboards, 100

patterns of, 363 Checkerboard test, 74–76 Checker placing, 79–81

practice effect in, 81

Choroid, 5, 6, 24, 33, 190, 289, 325–331, 369 Choroidal detachment, 19

Choroidal vessels, enlargement of, 329 Ciliary neurotrophic factor, 40, 42 Cis-2,3-piperidinedicarboxylate, 376

Clinical studies, 119–126 Clock cycle, 184 CMOS, 188

Cochlear implants, 48, 61, 62, 64, 222, 229, 256, 258, 319

success of, 61

Cochlear nucleus, 310, 311, 316, 319–321 implantation in, 319–321

Cognitive system, 91 Coil geometries, 280 Coils, 138–140, 172

coupling and loading of, 143 external and internal, 280 implanted, modeling of, 291–292 models of, 282–286

quality factors of, 139 Colliculus, 320

superior, 34 Color

discrimination of, 59 perception of, 124–126 stimulation of, 194

Color vision, 92

Compensation for a missing sense, 50–52 Compensation, neural basis of, 52–57 Compensatory hypertrophy, 56 Complementary metal oxide semiconductor

(CMOS), 151

Complications during surgery, 20, 25, 125 Computational challenges, 300–301 Computational modeling, 279–303 Computer-aided learning, 111

Cones, 6

Conjunctiva, 4, 5, 12, 13

Contrast sensitivity, testing of, 101, 103–104 Convection coefficients, 289

Conversion

digital to analog, 179–182 serial to parallel, 178–179

Cornea, 5, 8 Cortex, 91, 194

auditory, 52, 53, 56, 61–62 cerebral, 308–321 inferotemporal, 49 parietal, 54 somatosensory, 52, 53

visual, 48, 52, 53, 54, 95, 187, 319, 321, 347 Cortical areas, differences between, 47–50 Cortical auditory evoked potential after

cochlear implant, 61 Cortical mapping, 48

Cortical reorganization, 47, 54 Cortical resources, competition for, 64 Counting tasks, 75, 76, 77, 79, 81

Index 383

Coupling of coils, computation of, 282–286 Cross-modal influences, anatomical

substrates of, 55

Cross-modal plasticity, 51, 52, 54–57, 61, 64 in deaf individuals, 55–57

Cross-modal plasticity in restoration of a sense, 57

Cross-modal processing, interference with a, 55, 63

Cross-modal responses critical period of, 55

in sighted individuals, 55 tactile, 56

within right auditory cortex, 56 Cross-modal responsivity, 54 Crosstalk, 334, 343

Current densities, 265, 299

Current densities in the retina, 294–301, 302–303

Current injection, 293, 294

Current loops, decomposition of, 281 Current pulse stimulation (PS), 246 Current sources, 161, 295, 299 Current spread, 279, 301, 338 Current spread simulations, 301–302 Current stimulation thresholds, 334 Cyclic voltammetry, 246, 251

Data buses, 176 Data communication

bidirectional, 175, 185 wireless, 143–146

Data conversion, 179–181 Data rates, 144, 174

Data telemetry, 279 forward, 144–146 reverse, 146

Deafness, compensation for, 56 Decimal acuity, 92 Decimation algorithms, 198 Decoders, 176

Degradation, 2 Demultiplexing, 136–137 Densities, charge current, 334 Detachment

choroidal, 19

retinal, 1, 6, 12–13, 23, 24, 25, 125, 369 diagram of, 8

Diabetes mellitus, 13

Diabetic retinopathy, 13, 71, 120 Diagnostics, 10

Digital-to-analog current converters, 172, 179–181

Dining table scenery, 106–107

384 Index

Dipole electric potential, 260 Dipole moment, neuron, 358 Directshow, 73

Direct wiring, 245

Disciform macular degeneration, 15 Disease

retinal, 13–19 degenerative, 12, 13 vascular, 13

Double layer capacitance, 250 Duty cycle, 259

Edema, 119

Edge detection, 157, 199–200

Edge detection algorithms, 198, 201

Edge enhancement, 152, 156, 157, 158, 198 Edge enhancement algorithms, 198, 201 Edge following, 200

Electrical activation, neuroprotection by, 40

Electrical activity, cellular effects of, 39 Electrical current, 33, 35, 39, 117, 139, 326,

330, 342 Electrical damage, 2

Electrical evoked cortical potentials, 190–191, 192

Electrically elicited electroretinograms interpretation of, 376

pharmacological dissection of, 374–378 Electrically evoked potentials, 34, 36–38, 38,

41, 163, 326, 330 Electrically evoked response, 18

Electrical potential, distribution of, 266 Electrical potential across an interface, 211 Electrical stimulation, 111, 349

biological tissue, 252

differences from responses to light of, 371 effect of on the retina, 31

ganglion cell layer, 347 high-frequency, 340–342 perception after, 123

pH changes induced by, 232–240 response of the retina to, 366–378 retinal, 1, 72, 111, 116, 118, 126,

129, 210, 255 intraocular, 121 safety of, 119

safety of, 330

tissue damage by, 227 upregulation by, 40

Electrical stimulation therapy, 43 Electric fields

divergence of, 265–266 non-uniform, 374

Electric pulse train, 122, 347, 355, 373 Electrocardiogram, 358

Electrochemical characterization, 243–253 Electrochemical impedance spectroscopy,

246, 248 Electrochemical reactions,

263–265

at the electrode-vitreous interface, 211–218 Electrode arrays, 32, 36, 119

modeling of, 292–294 small, 369–370

Electrode-electrolyte interface, ph changes at, 232, 235

Electrode implantation, 38 Electrode materials, 218–219

electrical properties of, 211 Electrodes

addressing of, 165

biological environment, 159–161 capacitance of, 250–251 capacitative, advantages of, 213 charge-injection, 244

contact spiral cuff, 188 corrosion of, 252 counter, 39

current pulsed, 211 disk, platinum, 334 dissolution of, 213 epiretinal, 37

gold, 219, 244–245, 369, 371 intracortical, 307–321 iridium, 219, 244, 311

iridium oxide, 262, 263, 264–265, 311, 369 low impedance, 141, 219, 222 MEMS-based, 229

microbump, 169

nanopowder molding of, 244, 245, 246, 253 neurostimulatory, 212–213

optic nerve penetrating, 187, 188, 189, 191, 193, 194, 195, 197, 198, 203, 206

placement of, 190, 192, 193

platinum, 212, 213, 215, 217, 219, 222, 230, 244–245, 262, 264–265, 273–274, 325

dissolution rates of, 220 electrochemical characterization of,

243–253

molded, 245, 248, 251, 252, 253 electrical impedances of, 250 electrical resistivities of, 248

platinum–iridium, 219, 349 protruding, 269–270 recording, 190

placement of, 195

retinal prosthesis, 209, 210, 211, 212, 213, 219, 220, 221, 222, 223, 227, 255–275

operational stability of, 219–221 small-diameter, 333–343

stacked bump, 159–161, 162 stimulating, 32, 33, 36–37, 94

effects of reducing the size of all on charge density of, 353

placement of, 190 platinum, 236

stimulus, large scale integration, 151–167 subretinal, 38, 375

surface area of, 253 surface roughness of, 253 titanium, 244

Electrode stimulation, 230

Electrode surface area, effective, 221–223 Electrode test apparatus, 214–218 Electrode-vitreous interface, 211–218 Electroencephalograms, 358

Electromagnetic effects, modeling of, 279–303 Electrophysiological examinations, 92 Electrophysiological experiments, 156, 158,

161–162, 167

Electrophysiological tests, limited value of, 98 Electrophysiology, 355–379

invasive techniques of, 364, 373–374 noninvasive techniques of, 360–364, 373

Electroplating, 245

Electroretinograms, 10–12, 15, 16, 43, 92, 93, 360–364, 370–373

corneal, 367

electrically elicited, 374–378 focal, 362, 370–372 light-induced, 371

limits of, 12 mid-flash, 372–373 multifocal, 362–364

Encoders, 176 Energy density, 137

Epiretinal approaches, 19–23 surgical limitations of, 19–20

Epiretinal implants, 343 Epithelium, retinal pigment, 369 Everyday tasks

mastery of, 106 performance of, 105–107

testing of, 96 Evoked potentials, 35

Evoked responses, collicular, 35 Extracellular recordings, 358, 359, 364 Extracellular stimulation, passive model of,

259–261

Index 385

Extraocular units for wireless prostheses, 169–170

Eye

anatomy of, 2–9 anterior segment of, 3–5 physiology of, 2–9 posterior segment of, 5 stimulation of, 18

Eyeball

anterior structure of, 4 cross section of, 3

Eye disease, animal models of, 367 Eye dominance, 89

Faradaic charge flow, 252 Faradaic charging, 212 Faradaic processes, 263–265 Faradaic reactions, 214, 264 Faraday’s Law, 281 Fibrosis, 20

Field of vision, normal, 9 Field potential, 372

Field potential recordings, 358, 359 Filtering, spatial, 156

Fine wire probes of the eye, 364 Finger counting, 39, 97

definition of, 32

Fingers, smearing of information across, 53 Firing rate, 161–162, 364, 373

Flexibility of stimulation, 144 Flickering, 18, 99, 133, 136, 308 Fluorescein angiogram, 9–10 Fluorescent dye, 41

Focal electroretinograms, 362, 370–372 Fourier’s Law, 287

Frame rate, 170

Freiburg Visual Acuity and Contrast Test (fract), 98, 103–104

Frequency limitation, 154–155 Frequency of stimulation, 337

Functional magnetic resonance imaging, 48, 50–51, 53, 54, 59, 60

Functional mapping, 359 Fundus, 9, 15

appearance of, 15 diagram of, 6

Fundus photo, 10

GABA, 365

Gain, electrical, 360

Ganglion cell layer, 17, 23–24, 34, 347, 368 retinal, 373

386 Index

Ganglion cells, 6, 16–17, 21, 111, 114, 188, 257, 258, 274, 275, 280, 301, 333–343, 365

measuring the activity of, 363 protection of, 40

spiking of, 364

early and late phases of, 352–353 Glaucoma, 5, 20, 120, 307

Glial tissue, 32 Gliosis, 20, 25

Glutamate - aminobutyric acid, 365 Glutamine synthetase, 42

Gold, 159–160, 161, 162, 219, 244–245, 369, 371

Gradiant filters, 200

Grating acuity, assessment of, 102–103, 104–105

Grating acuity test, 98 Gray level, 181

pixel, 170

Hand dominance, 89

Hand–eye coordination, 81–83, 85 Hearing, blind individuals’ abilities for, 51 Heat

diffusion of, 262 dissipation of, 204, 291–292 metabolic, 287

radiated, 172

Heating of tissues, 245, 261–263

Higher visual areas, neuronal responses in, 54 Histogram equalization, 199, 201

Hydrogels, 21

Hydrogen evolution, electrolytic, 216, 218 Hypertension, 13

Hypertrophy, 329 compensatory, 53–54

Hypotony, 19

IGF-1, 40, 41, 42

IIP retinal implant system, 111–126 Image acquisition, 197–198

Image processing, 91, 156–159, 273 adjustable, 258 location-dependent, 258, 274–275 retinal, 132

Image-processing algorithms, 188 Image-processing strategies, 198–202 Image projection, 269–273

Image quality, 115 Impedance method, 295–300

simulation of, 295–303 Impedance networks, voxel, 298–299

Implantation

cochlear nucleus, 319–321 electrode, 38

microelectrode array, 210, 227 microelectronic device, 21–23 microstimulating array, 311 retinal prosthesis, 162–167 subretinal, 23–25, 151, 257 suprachoroidal, 151

surgical procedures for, 36–37 Implantation in the eye, 19, 21–25 Implant design, limiting factors on, 2 Implants

cochlear, 40, 61, 62, 64, 222, 229, 256, 258, 319

common qualities of, 1 epiretinal, 111, 343 intraocular, 227

issues with, 2 microarray, 169–186 ocular, 1 optoelectronic, 273–274 retinal, 19–25, 111–126 subretinal, 171, 255

wireless-microarray, 169–186

Inductive coupling, 138–139, 279, 280–283 Inductive radiofrequency transmission, 274 Inferotemporal cortex, macaque, 49 Information encoded at the retinal level, 93 Information flow, 365

Information gathering, 355 Information processing, 114 Information transmission, 269–275 Infrared data transmitter, 114 Inner limiting membrane, 41

Inner nuclear layer, 6, 17, 23–24, 34 nuclear condensation of cells of, 329

Insulin-like growth factor–1, 40, 41, 42 Interface, electrode-vitreous, 211–218 Interference, 259

telemetry, 145 Interphase interval, 133

Intracellular recording, 358, 359

Intracortical microstimulation (ICMS), 307–321 Intraocular pressure, 2, 5, 12, 19, 20–21

factors affecting, 21 Intraocular probes, 13, 18

Intraocular units for wireless prostheses, 169–170

Iridium, 161, 219, 244, 311, 349 Iridium oxide, 160, 219

electroplated, voltammogram of, 236 redox reaction mechanisms of, 236–237

Iris, 2, 3–4, 272

Japanese Consortium for an Artificial Retina, 31

Joule heating, 287

Kernel weight, 157

Language processing, 52 Large-scale integration, 151–167 Lateral geniculate nucleus, 39 LCD displays, 270

infrared, 255

Learning, computer-aided, 111 Learning effects, 62–63, 81

visual, 48

Learning processes, 49–50, 116 LED illumination system, 272–273 Lens, 5

artificial, 5

Light, localization of, 100–101 Light-evoked potential, 194–197 Light perception, directional, 97 Light power, 272

Light responses, duplication of, 347–351 Light sensitivity, 92, 93

Limbus, 12, 22, 24, 36

Local field potential, 357–358 Local field potential recording, 359 Localization of light, testing

of, 100–101

Low vision enhancement system, 72–73

Macula lutea, 308 Macular chip design, 258 Macular degeneration

age-related, 14–15, 18, 71, 111, 120, 129, 170, 209, 255–256, 280, 334, 347

disciform, 15 dry, 14, 15 incidence of, 14 neovascular, 14 remapping in, 48 treatments for, 15 wet, 14

Magnetic resonance imaging, 48, 50–51, 53, 54, 59, 60

Magnetoencephalography, 56 Materials, 1, 244, 335

adhesive, 245 biocompatibility of, 119 electrode, 218–219

charge capacity of, 117 polyimide, 162

Index 387

Materials science, 209–224 Mechanical damage, 2

Membrane potential, changes in, 374 Metabolic heat, 287

Microarray implants, 169–186 Microchip arrays, 162–166 Microchips, distributed, 162–166 Microelectrode arrays

high-density, 244 implantation of, 210, 227 planar, 236

Microelectrodes, 111–112, 114, 116, 183 fine wire, 364

intracortical, formation of, 310 iridium oxide, 212

metal, 213

production techniques for, 245 stimulating, 307–321

tissue responses to, 311–321 Microelectronic devices, 17

implantation of in eye, 21–23 Microfabrication, 369

thin-film and MEMS, 239 Micromachining, 245 Micromanipulator, robotic, 373 Microneuromas, 17 Microphotodiode arrays, 23–25

Microstimulating arrays, implantation of, 311 Microstimulation with intracortical electrodes,

307–321 Mobility trainers, 106 Modeling

component, 289–294 electromagnetic effects, 279–303 extracellular stimulation, 259–261 numerical methods for, 301 thermal effects, 279–303

Models

2-D vs. 3-D, 300 computational, 379 layered retina, 295 multi-resolution, 300 sparse-matrix, 301

Molding, nanopowder, 243 Molyneaux’s Question, 57–62 Monophasic waveforms, 214 Motion, detection of, 97, 101 Motion processing, 53, 59

differences in, 51–52 Müller cells, 8, 17, 41

Multi-electrode arrays, 189, 336 Multi-electrode stimulation, simultaneous,

340–341, 343

Multifocal electroretinograms, 363–364

388 Index

Multiplexed signal, 184

Multiplexing techniques, 172, 185

Mylar films, 267

Nanoparticles

molding of, 243, 244, 245, 246–253 platinum, 246

Nernstian equation, 237 Nerve cells, 111

electrical stimulation of, 17–19 Neural cells, 269

retinal, 260

electrical stimulation of, 257 Neural circuits, 256, 307

Neural damage, threshold of, 330 Neural encoder, 198

Neural injury, 319 stimulation-induced, 212

Neural interface, 188

Neural network of the retina, 365 Neural prostheses, 227

implantable microelectronic devices for, 243 intracortical microstimulation, 309–311

Neural recording, 244 Neurological stimulation, 243–253

Neurons, 17, 34, 49, 54, 62, 184, 258, 309 cortical, 311

electrical activity of, 39 first-order, 373

injury to, 312–316

lateral geniculate nucleus, 39 populations of, 373, 375 post-synaptic, 365

relative order of, 374 retinal, 8, 355, 370

spike timing between, 348 secondary, rewiring of, 72 third-order, 376

visual, 274 Neuroprotection

electrically induced, 32, 39–43 transcorneal electrical stimulation

induced, 41 Neurostimulator, 121

N -methyl-D-aspartic acid, 375–377

Obstacles, detection of, 106

Occipital responses, functional role of, 55 Ocular dimensions, average, 8–9

Ocular implants, 1 Ohm’s Law, 287, 298

Optical coherence tomography (OCT), 10 Optical information, acquisition of, 91

Optical projection, direct, 258 Optic nerve, 6, 21, 34, 41, 95, 355

axons of, 188, 308

electrical stimulation of, 189–206 testing of, 95

transection of, 40, 41

Optic nerve sheath, 191, 193, 194, 195–196 Optoelectronic implants, design of, 273–274 Orbital cavity, 3

components of, 2 Orientation, testing of, 107 Outer nuclear layer, 6, 16

Outer nuclear layer cells, irregular, 329

Paired-flash electroretinograms, 362–363 Parietal cortex, 54

Partial inductance method, 279, 281–283 simulation of, 282–286

Parylene, 244, 310

Pattern electroretinograms, 363 Patterns

recognition of, 59

temporal, retinal light-response, 347–353 Perceived objects, size of, 124

Perception, flickering/non-flickering, 18, 99, 133, 136, 308

Percepts, 308, 356

Perceptual threshold, definition of, 122 Perfluordecaline, 119

Perforated membranes, 268–269 Perimetry, 92

Peripheral vision, loss of, 21

Pharmacological dissection, 365–366, 374–378 pH changes

monitoring of, 229, 236 stimulus induced, 227–240

typical, 235

pH effects, minimization of, 240 pH electrodes, 229

calibration curves for, 237–238 iridium oxide, 236

micro, potential response of, 238 microarray, 230

thin-film construction of, 237 miniaturization of, 239 solid-state, advantages of, 239

pH measurements, 230–231

Phosphenes, 18, 33, 36, 40, 72, 84, 187, 257, 308, 319

Phosphene vision, simulated, 76 Photic stimulation, 195, 360 Photodynamic therapy, 15 Photolithography, 269–270, 369 Photoreceptor cells, 151, 161, 209

Photoreceptor damage, 210 Photoreceptor nuclei, 17 Photoreceptor response, 362

Photoreceptors, 6, 111, 114, 188, 274, 329, 365, 372, 377

degenerated, 33–34 Photosensitivity, variable, 155–156 Photosensors, 151

pH profiles, 2-D distributions of, 238–239 Physiology of the eye, 2–9

Pigment coding, 119

Pitch, changes in, identifying, 51 Pixel density, 257–258

Pixelized conditions, 74, 75, 81, 83, 85, 88 Pixel number, 211

Pixel spacing, 265–266 Plasticity

cross-modal, 52, 54–57, 61, 64 in deaf individuals, 55–57

increase of across the visual hierarchy, 49, 62 neural mechanisms underlying, 50

sensory, 47–50

Plasticity and age of deprivation, 62 Platinum, 159–160, 161, 162, 212, 213, 215,

217, 219, 222, 230, 244–245, 248, 250, 252, 262, 264–265, 273–274, 325

nanoparticles of, 246 Platinum black, 245 Platinum gray, 222–223 PMMA, 1, 5

Pocket processor, 112, 114 Poly-dimethylsiloxane, 244, 246 Polyimide, 244, 369 Polymethyl metacrylate, 1, 5 Polyurethane, 327

Power consumption, 135, 172, 204, 274 Power conversion, 175, 176–177

efficiency of, 140, 177–178 Power delivery, wireless, 138

Power deposition in tissue, 283, 285–287 Power dissipation, 204, 263, 291–294 Power requirements, 137–138

Power supplies, 174, 274

Power transfer efficiency, 140–141 Power transmission, 269–275, 279

wireless, 138–143, 169

Power used by retinal prostheses, 131–132 Practice effect, 81

Preclinical studies, 119

Pressure effect on the retina, 20–21 Projection system, 269–273 Prostheses

dual-unit, approach to, 280 epiretinal, 32, 210

Index 389

history of, 1–2 retinal, 347

all-intraocular, 21–23 diagram of, 22 design of, 178–184 development of, 357

dual-unit, 279–303 flexibility of, 131–132

high-resolution, 129–147, 255–275 implantation of, 162–167 intraocular, 1–25

early model of, 228 materials for, 1

power used by, 131–132 size constraints of, 213 size of, 131–132

subretinal, 32 visual

design of, 197–203 electronic, 209 epiretinal, 343 ICMS, 307–321

pH changes in, 227–240 resolution of, 334

Prosthesis wearers, training methods for, 86 Prosthetic devices

interference with cross-modal processing by, 55

retinal, 162–167, 209–224, 347 all-intraocular, 21–23 dual-unit, 279–303

high-resolution, 129–147, 255–275 intraocular, 1–25

materials for, 1

power used by, 131–132 Prosthetic stimulation, 347–353 Prosthetic vision, modeling of, 71–89 Proximity, cell-electrode, 258, 259–266 Pseudocapacitive voltage step, 262

Psychometric threshold, definition of, 105 Psychophysical testing, 96, 97–105

elements of, 98

technical setup for, 98–100

Pulse amplitudes, 190–191, 193–194, 202 Pulse configuration, 214

Pulse duration, 190–191, 193–194, 202 Pulse frequency, 202

Pulse frequency modulation, 151

Pulse frequency modulation image sensor, 154 Pulse frequency modulation photosensor,

152–162

modification of, 154–156 Pulses

biphasic, 134, 262, 273, 292, 308, 327, 349