E. de Juan

A neuro-stimulus chip with telemetry unit for retinal prosthetic device

In this retinal prosthesis project, a rehabilitative device is designed to replace the functionality of defective photoreceptors in patients suffering from retinitis pigmentosa (RP) and age-related macular degeneration (AMD). The device consists of an extraocular and an intraocular unit. The implantable component receives power and a data signal via a telemetric inductive link between the two units. The extraocular unit includes a video camera and video processing board, a telemetry protocol encoder chip, and an RF amplifier and primary coil. The intraocular unit consists of a secondary coil, a rectifier and regulator, a retinal chip with a telemetry protocol decoder, a stimulus signal generator, and an electrode array. This paper focuses on the design, fabrication, and testing of a microchip which serves as the telemetry protocol decoder and stimulus signal generator. It is fabricated by MOSIS with 1.2-mm CMOS technology and was demonstrated to provide the desired biphasic current stimulus pulses for an array of 100 retinal electrodes at video frame rates.

Electrical stimulation of retina in blind humans

A prototype electronic retinal prosthesis has been tested in two subjects. The system features an implanted retinal stimulator and an external system for image acquisition, processing, and telemetry. Subjects can perceive light when each of the 16 electrodes were activated. Stimulus thresholds ranged from 28 to 1417 /spl mu/A. Strength duration curves were obtained in all two subjects. Dynamic range for the brightness of the stimulus was demonstrated. Using the camera, the subjects were able to locate objects and determine the direction of movement.

Intraocular retinal prosthesis test device

Abstract : There is a growing interest in the development of a retinal prosthesis device based on a number of successful experiments that have demonstrated electrical stimulation of retinal tissue. An introcular retinal prosthesis test device is currently under development at NRL/JHU. The general approach and technology development issues are discussed as well as some neurophysiology interface issues. The final device will enable acute human experiments in an operating room environment.

An implantable power and data receiver and neuro-stimulus chip for a retinal prosthesis system

In certain diseases of the retina, the photoreceptor cells do not respond to light and thus cause blindness. We describe an electronic retinal prosthesis system that can provide some vision to patients by direct electrical stimulation of the retinal neurons. Power and image data are transferred to the implanted stimulator through a wireless inductive link. The system consists of an external video camera with image processing and encoding hardware and a power and data transmitter. Implanted in the eye are power and data receivers, stimulus circuits, and electrode array. The most recent prototype implant device, implemented in 1.2 micron CMOS, implements demodulation and decoding of the data stream and produces biphasic current stimulus pulses for an array of 100 retinal electrodes at video frame rates.

Clinical results with the model 1IRP implant

This paper discuss the feasibility study of implanting an epiretinal prosthesis in humans with bare or no light perception vision from retinitis pigmentosa. Patients were implanted with a Second Sight intraocular epiretinal prosthesis in the eye with worse vision. The implant consisted of an extraocular microelectronic device and an intraocular electrode array, connected by a multiwire cable. At the end of the procedure, it was concluded that all the subjects could see visual perceptions that correlate to electrical stimulus from a chronically implanted retinal prosthesis. Patients used a camera driven stimulus to perform simple tasks.

Chronic electrical stimulation of the canine retina

An electronic retinal prosthesis is under development to treat retinitis pigmentosa and age-related macular degeneration, two presently incurable diseases of the outer retina. Previous studies have established the feasibility of the retinal prosthesis. The goal of these experiments was to investigate chronic stimulation of the retina. These effects were measured by direct examination of the implant, electrophysiology of the retina, electrically elicited responses, and examination of histology post-implant. Implants were placed in 6 dogs. The implant featured an implantable stimulator and a 4/spl times/4 array of 460-micron diameter platinum disks positioned on the retina. 6 dogs were chronically stimulated at 0.05 mC/cm/sup 2/ and 0.1 mC/cm/sup 2/ for up to 60 days (10-12 hours/day). No retinal damage was evident from the stimulus. Some mechanical damage of the retina due to array misalignment was apparent in early implants, but this was minimized with improved surgical technique. Bright flash electroretinograms showed no changes in retinal function comparing pre and post implant recordings. Electrically evoked cortical responses were recorded from 1 dog showing that the functional connection between the retina and the remained. Histological analysis revealed normal retina under the array of 1 dog that had been stimulated for 25 days.

Cortical response after chronic electrical stimulation of canine retina

Electrical stimulation of the canine retina (in normal and RCD1) is carried out. An electronic retinal prosthetic chip is implanted which contain an implantable stimulator and 16 platinum electrodes disks of 460/spl mu/ diameter placed on the retina. Three dogs were chronically stimulated at 0.05 mC/cm/sup 2/ and 0.1 mC/cm/sup 2/ for 120 days (8-10 hours per day). Bright flash electroretinograms (ERGs) were recorded on the three dogs and found no recordable ERG from a blind dog. After completion of the stimulation protocol cortical subdural electrodes were implanted to record the cortical response for the electrical stimulation of the retina. The aim of this study is to evaluate the electrical evoked cortical responses in normal and blind dogs implanted with subdural electrodes.