Medical Design Briefs - April 2021 - 42

GlobAl

INNOVATIONS

Wireless Retinal Implant Restores Visual Field for the Blind
EPFL, Lausanne, Switzerland

PFL researchers have developed
dle, the researchers chose to work with
a new type of retinal implant for
an extremely flexible material. This
people who have become blind
enables the implant to be folded durdue to the loss of photoreceptor cells
ing surgery, so a larger implant can be
in their retinas. The implant partially
inserted without having to lengthen
restores their visual field and can sigthe incision. The material is a transparnificantly improve their quality of life.
ent, nontoxic polymer that is already
Thirty-two million people around
used in the medical field. " Because the
the world are blind. Between 2 and 4
polymer is flexible, the implant can
million of them owe their condition
bend to the curvature of the eye and
to the loss of light-sensitive cells in
be in greater contact with the retinal
their retinas. The most promising
ganglia, " says Marta Airaghi Leccardi,
The retinal implant is designed for people who have become
treatment for this type of blindness is blind due to the loss of photoreceptor cells in their retinas. another PhD student at the LNE.
a retinal implant containing elec- (Credit: EPFL)
■ Photovoltaic Pixels and No
trodes that electrically stimulate the
Wires
retinal cells. " But current implants
The researchers were able to make
produce very poor results, and their
60 Px
1200 Px
2300 Px
20,000 Px
their implant wireless by replacing the
wearers are still considered legally
electrodes with photovoltaic pixels.
blind, " says Diego Ghezzi, who holds
Unlike electrodes, the solar-powered
the Medtronic Chair in Neuropixels generate an electric current
engineering (LNE) in EPFL's School
themselves and do not require an
of Engineering. " In order to lead
60 Px
1200 Px
2300 Px
20,000 Px
what is considered a 'normal' life, the The same image looks very different, depending on how external energy source. The light captured by the camera therefore no
implantee must recover a visual field many pixels are available. (Credit: EPFL)
longer needs to be transformed into
of at least 40°. Current implants
tailed the patterns, the easier it is for the
electrical signals. Instead, it needs to be
achieve only 20°. "
wearer to recognize them.
magnified in order to be detected and
The LNE researchers have come up
processed by the photovoltaic pixels. " The
with a pioneering, wireless implant made
■ Larger Surface Area Means
pixels will only react to light signals that
of a highly flexible and pliable material
More Pixels
meet certain requirements in terms of
and containing photovoltaic pixels. It is
EPFL's implant, like conventional
intensity, duration and wavelength, " says
expected to provide wearers with a visual
implants, is composed of an array of pixFerlauto. " Natural light alone isn't
field of 46° along with much better resoels, glasses, and a camera - but no wires.
enough. " A second advantage of photolution. These findings were published in
It also has a larger surface area designed
voltaic pixels is that they take up less space
Nature Communications.
to widen the visual field and improve
than electrodes. More of them can fit on
image quality. The greater size also
the implant, which further boosts both
■ Poor Results from Existing
means that more retinal cells will be stimvisual acuity and the field of vision.
Implants
ulated by the photovoltaic pixels. " This
In the first round of tests, the protoThe retinal implants currently available
will expand the field of vision, " says Laura
type proved to be nontoxic and to succonsist of a grid of electrodes placed
Ferlauto, a scientist at the LNE. " Existing
cessfully increase the visual field and visudirectly on the retina. The implants are
implants only stimulate cells at the center
al acuity. The next step will be in vivo triwired to a pair of glasses and a camera and
of the retina. " Naïg Chenais, a PhD stuals to look into other factors such as how
to a portable microcomputer. The camera
captures images that enter the implantee's
dent at the lab, adds, " It also means we
the pixels behave and how long the imfield of vision and sends them to the comcan increase the number of photovoltaic
plant will last. " It will also be interesting
puter, which turns them into electrical sigpixels, which will sharpen the images. "
to see how well humans adapt to this new
nals that it transmits to the electrodes. The
way of seeing, which is unlike our natural
electrodes stimulate the retinal ganglion
■ Surgical Constraints
vision, " says Ferlauto.
cells based on the light patterns detected
Until now, the size of retinal implants
This article was written by Clara Marc,
was limited mainly by the length of the surin the field of vision. The implantee then
EPFL. A video of the technology is available at
gical incision in the eye. " The cut has to be
has to learn how to interpret the incomhttps://www.youtube.com/watch?v=
as small as possible to avoid damaging the
ing visual sensations in order to 'see' the
ZURkvJOG4m4&t=12s. For more informatissue, " says Chenais. To get past this hurimages. The more numerous and detion, visit https://actu.epfl.ch.

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Medical Design Briefs, April 2021

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Medical Design Briefs - April 2021

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