Biomedical Engineering Reference
In-Depth Information
1
High-Resolution Opto-Electronic
Retinal Prosthesis: Physical
Limitations and Design
D. Palanker, A. Vankov, P. Huie, A. Butterwick, I. Chan, M.F. Marmor
and M.S. Blumenkranz
Department of Ophthalmology and Hansen Experimental Physics Laboratory,
Stanford University
Abstract:
Electrical stimulation of the retina can produce visual percepts in blind
patients suffering from macular degeneration and retinitis pigmentosa (RP).
However, current retinal implants provide very low resolution (just a few
electrodes), whereas many more pixels would be required for a functional
restoration of sight.
This article presents a design of an optoelectronic retinal prosthetic
system with a stimulating pixel density of up to 2500 pix/mm
2
(corre-
sponding geometrically to a maximum visual acuity of 20/80). Requirements
on proximity of neural cells to the stimulation electrodes are described as
a function of the desired resolution. Two basic geometries of subretinal
implants providing required proximity are presented: perforated membranes
and protruding electrode arrays.
To provide for natural eye scanning of the scene, rather than scanning with
a head-mounted camera, the system operates similarly to “virtual reality”
devices. An image from a video camera is projected by a goggle-mounted
pulsed infrared LCD display onto the retina, activating an array of powered
photodiodes in the retinal implant. The goggles are transparent to visible
light, thus allowing for the simultaneous use of remaining natural vision
along with prosthetic stimulation. Optical delivery of visual information
to the implant allows for real-time image processing adjustable to retinal
architecture, as well as flexible control of image-processing algorithms and
stimulation parameters.
Introduction
As the population ages, age-related vision loss from retinal diseases is becoming
a critical issue. Two retinal diseases are the current focus of retinal prosthetic
work: retinitis pigmentosa (RP) and age-related macular degeneration (AMD).
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