Microchip Implant Could Offer New
Kind of Vision
Source: The Irish Times
November 9, 2000
US medical researchers, electronics experts and software
designers who have been working together now believe they can help the
blind to see. Dick Ahlstrom reports on their remarkable efforts Giving
sight to the blind might sound like something out of the Bible, but a
group of scientists are quietly confident that it is a gift they can
deliver.
Medical researchers, electronics specialists and
software designers have joined forces to develop a microchip that can
be implanted inside the eye, providing a new kind of "vision". The
scientists admit it will probably be very different from ordinary
sight but it could allow the blind to get
about more easily, recognise faces and perhaps read.
A member of the research team, Dr Mark Humayan of Johns
Hopkins University, was in Dublin recently to describe the work and to
explain how it might help those with irreversible loss of vision
caused by diseases such as retinitis pigmentosa (RP) and age-related
macular degeneration (AMD). He was the
guest of the Irish branch of the international organisation, Fighting
Blindness, which raises funds for research into blindness.
The work is attracting a great deal of attention and has
been given a high media profile through the support of celebrities
such as the musician and composer Stevie Wonder. He has allied himself
with the work and helps promote it in the US.
Intensive research on an "intraocular retinal
prosthesis" is under way at three centres in the US at Johns Hopkins
University, North Carolina State University and at Second Sight Ltd of
California. It dates back 10 years when a team began collaborating on
the development of a purpose-built
microchip that could be mounted inside the eye.
The retina is made up of a complex of cells which, in
the healthy eye, delivers an electric signal via the optic nerve to
the vision centres of the brain. The photoreceptor cells, the rod and
cone cells, which respond to the light, sit at the back of the retina.
These are damaged or lost in patients
with RP or AMD, so vision is impaired. Dr Humayan's research showed,
however, that the cells behind the photoreceptors remained active and
could deliver a signal to the brain.
He led research which showed that if electricity was
applied to the back of the eye, the stimulation would create a visual
signal in the brain which a blind person could "see". The hope is that
if a microchip implanted on the retina could deliver the electrical
stimulation in a co-ordinated way then
perhaps a sort of vision could be returned.
Dr James Weiland, professor of ophthalmology at Johns
Hopkins and a member of the research team, says the vision system
includes a camera mounted in specially built eyeglasses; computer
software which processes what the camera sees; a radio transmitter;
and an implanted antenna that both carries the radio signal to a chip
mounted on the retina and provides power
for the chip.
"We were trying to simplify the type of system that is
implanted," Dr Weiland explained. The team wanted to keep patient
disturbance to a minimum, he said, so the only surgery involves
attaching the microchip to the retina. The camera and software can be
replaced or upgraded without affecting
the patient.
Surprisingly, most of what the team needs to advance the
project is already available in other electronic devices. "We are
relying on consumer electronics to move things along," Dr Weiland
said.
The "wireless antenna", which appears in the
accompanying drawing as a ring at the front of the eyeball, is already
used in cochlear implants, which help give some hearing to those with
profound hearing loss. And the special glasses use a common CCD
camera.
The chip and its "packaging" - required to protect the
delicate electronics when inside the eyeball - were a "technical
challenge" that had yet to be overcome, Dr Weiland said.
The research team has yet to implant a working chip, but
it knows how the overall system would work. The person would wear the
glasses and the CCD camera would deliver a "picture" to the computer
software. The software would convert the picture into a digital
signal, transmitting this to the
antenna implanted in the eye for relay to the chip.
The chip would then deliver a co-ordinated electrical
impulse to the retinal surface. The rear of the microchip has an array
of 60 electrodes organised into a grid of rows and columns. These
electrodes, which measure about half a millimetre across, are designed
to stimulate the tissues behind the rods and cones.
"You would make a pattern and the chip would route the
correct signal to the correct electrode," Dr Weiland explained. The
electrical stimulation send a signal to the vision centres of the
brain, which the researchers believe will give a new form of sight.
How good would the newfound vision be? Initially quite
crude, Dr Weiland believes, although even a 60-pixel chip would be an
immediate aid to mobility for a blind person. "As the technology
improves we will get more and more visual acuity. The progression is
probably going to be from a crude device that gives shape
recognition."
As the number of chip electrodes increased, more
definition would become available. "We certainly want to go to a
higher number but we are limited by the technology. You would need
1,000 electrodes to achieve face recognition."
It would be some years before the first chips are
mounted inside humans, he added. He believes a working system will be
approved by the US Federal Drug Administration (FDA) and installed in
patients within a decade.
Fighting Blindness is an organisation dedicated to the
discovery through research of treatments and cures for all forms of
blindness. More information about its work is available on its website
at
www.fightingblindness.ie
http://www.ireland.com/newspaper/science/2000/1109/sci1.htm