Interfacing Microelectronics and the Human Visual System - Biomimetics: Biologically Inspired Technologies - page 427

17

Interfacing Microelectronics
and the Human Visual System

Rajat N. Agrawal, Mark S. Humayun, James Weiland,
Gianluca Lazzi, and Keyoor Chetan Gosalia

CONTENTS
17.1 Introduction ........................................................................................................................................ 427
17.1.1 Cortical Prosthesis ............................................................................................................... 428
17.1.2 Concept of Retinal Prostheses............................................................................................. 429
17.1.3 Optic Nerve Prostheses ....................................................................................................... 430
17.1.4 Sensory Substitution Devices.............................................................................................. 430
17.2 Current Concepts in Retinal Prosthetic Devices................................................................................ 430
17.2.1 Simulations of Prosthetic Vision......................................................................................... 432
17.3 Mechanical Effects of Implantation of Retinal Prosthesis ................................................................ 432
17.3.1 Infection and Inflammation ................................................................................................. 432
17.3.2 Ocular Side-Effects of Long Term Implantation................................................................ 433
17.3.3 Attachment of the Implant to the Retina ............................................................................ 433
17.3.4 Hermetic Sealing of the Electronics ................................................................................... 434
17.4 Electrical Considerations in Retinal Prosthetic Devices ................................................................... 434
17.4.1 Stimulating Electrodes: General Considerations with Regard
to Electrical Stimulation of the Retina ............................................................................... 434
17.4.2 The Impedance Method for the Solution of Quasi-Static
Electromagnetic Problems................................................................................................... 435
17.5 Retinal Prosthesis and Related Thermal Effects................................................................................ 436
17.5.1 Heat and the Telemetry System .......................................................................................... 439
17.5.2 Power Dissipation of Implanted Electronics....................................................................... 440
17.6 Future Implications............................................................................................................................. 442
17.7 Summary............................................................................................................................................. 443
References....................................................................................................................................................... 443

17.1 INTRODUCTION

Vision is an enormously complex form of information processing that depends on a remarkable
neuroprocessor at the back of the eye called the retina (Figure 17.1). For an intelligent living being
to see, every component of this complex system has to work in tandem. Blindness can result when
any step of the optical pathway — the optics, the retina, the optic nerve, visual cortex, or other
cortical areas involved in the processing of vision — sustains damage (Zrenner, 2002).

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