Processing the scene
Working with Second Sight, Humayun
and his colleagues started to develop the
Argus Retinal Prosthesis System, which
is named after Argus Panoptes, the
100-eyed giant from Greek mythology.
Although the Argus system does not consist of 100 eyes, it does have a few parts.
;e external parts consist of glasses
and a video processing unit. ;e glasses
include a small, o;-the-shelf video
camera that sits over the bridge of the
person’s nose. ;e camera captures the
scene and sends that information to the
video processing unit, which converts
the data into a pattern for retinal stimulation. ;is unit is about as big as a deck
of cards, and it includes a rechargeable
battery that powers the entire system.
It can also be turned on and o; by the
user, and it provides adjustments for
brightness and di;erent video settings
to, say, enhance contrast.
;e processed information goes back
to the glasses, where a wireless transmitter sends the stimulation pattern to an
antenna that is implanted on the eyeball
under the skin. ;e antenna connects to
a roughly pill-sized electronics package on the side of the eye, which sends
the electrical stimulation to an array of
electrodes attached—literally tacked—to
the retina at the back of the eye. For
the array, imagine a square of plastic
wrap that is just 5 mm on a side. ;ese
electrodes are designed to stimulate a
Pilot tests showed
that using a small
probe to provide very
low-level electrical
stimulation to the
retina succeeded. The
patients saw flashes
of light connected to
the stimulation.
pattern of activity in the retina’s ganglion cells, which then pass that information to visual areas in the brain.
;is system, in essence, converts
information from the video camera
into a pattern of stimulation on the
retina, which produces visual sensations, called phosphenes, that a person
can learn to interpret.
Although putting the processing
stages outside the eye means that the
user has to make head movements—
instead of just eye movements—to
change what is being seen, the outside
approach o;ers some benefits. “;is way,
you can upgrade the system outside the
body, taking advantage of advancements
in electronics and image processing,”
says Brian Mech, Ph.D., vice president
of business development at Second Sight
Medical Products. “We’ve changed our
video processing unit 12 times already.”
A further advantage is that the heat-pro-ducing processing is outside the body.
Reaching for regulatory approval
Moving from R&D to therapy requires a
series of clinical trials. Second Sight ran
the first one in 2002, using the Argus I,
which included only 16 electrodes in the
stimulatory array attached to the retina.
;en, the company created the Argus
II, a 60-electrode version, which is what
Barbara Campbell received. ;is device
went into clinical testing in 2006.
After a 30-patient clinical trial with
the Argus II, it received approval for use
in Europe in February 2011. According
to Mech, “In the U.S., we are anticipating FDA approval in 2012.” ;e device
costs about $100,000, and the surgery,
hospitalization and rehabilitation add
another $15,000– 20,000. Moreover,
simply getting the system surgically
implanted is not the end of the process,
which is the reason for rehabilitation.
;e patients need to relearn to interpret
light sensations and to adjust the Argus
system to their own preferences.
;e 30 clinical-trial patients reveal
the possible results. “Every one of them
could see spots of light,” says Mech,
“but that’s not all.” Everyone wants the
patients to get more than that, and they
did. All but one of them could locate
objects and more than half of them
could detect the direction of something
moving. About 80 percent of them could
even recognize letters, as long as they
were very big—say, taller than a soda
can. Perhaps most amazing of all, says
Optic nerve
Receiver
Tack
Electrodes
(Left) Courtesy of Second Sight Medical Products. (Right) John Newhart/Source Second Sight Medical Products
(Left) A glasses-mounted camera and external electronics convert video information into signals that can be transmitted into a device
that is surgically implanted in the eye. (Right) An antenna from the external device connects to a pill-sized receiver on the side of the eye,
which sends electrical signals indicating light and dark to an array of electrodes tacked to the retina at the back of the eye. The electrodes
stimulate activity in the retina’s ganglion cells, which pass that information through the optic nerve to the visual areas of the brain.
