European Blind Union
10th general assembly, London, UK, 26/28 October 2015
vision beyond the retina chip
Christina Fasser
Retina International, Ausstellungsstrasse 36, CH-8005 Zürich
cfasser@e-link.ch
Artificial vision is one of the most fascinating research fields: it
includes basic knowledge of the functioning of the retina, technical
knowledge of circuitry and finally the process of perception of
vision. At present artificial vision aims to patients that are fully
blind, but have an intact optic nerve. Very little research is aimed to
stimulate directly the cerebral cortex, i.e. the region in our brain.
This means that the main group of people that may benefit of this
research are people with retinal degenerative diseases such as
Retinitis pigmentosa (RP) etc.
Two artificial vision systems are on the market at present.
The research started roughly 20 years ago, mainly in Germany. In
that time, the Federal Ministry of Research granted more than 12
million D-Mark to initiate the research in Germany. Early 2000 the
Americans also started to fund this research area heavily. Two
systems received the C-Mark and are at present reimbursed in
Germany, Belgium, Italy and the USA: The first one, the ARGus 2
system is a so called epi-retinal system and uses a camera, a
computer system for data treatment and an electrode of 64
electrodes sitting on the retina, whereas the other system is a subretinal system, that is placed in the sub retinal space where the
original photoreceptors were sitting. The second system is relayed
to a battery sitting behind the year, similar to a cochlear implant.
The later system uses the "natural pathway" of vision. According
the patients that have been implanted, their vision resembles more
to the vision of a very heavily vision impaired person, whereas the
first system produces an artificial vision consisting of phosphenes.
People with the Argus 2 system need about four months training to
learn to interpret the light impulses and to regulate the system,
whereas with the sub-retinal implant people see much quicker. the
sub-retinal system has at present a shorter life-time, but it is hoped
that this will be improved shortly.
The success of the two implants varies among the implanted
patients. At present it is a mobility aid that is adding to the
techniques learned during the rehabilitation process. All among us
that became blind after a long process of degenerating vision do
know the difference between very small sight and no sight at all and
can appreciate that having a small perception might give a huge
difference to mobility and daily living skills.
In this respect clinical endpoints for artificial vision have changed
with the time. Earlier, it was hoped to be able to read directly wih it,
but the experience of the testing persons showed that it has at
present a higher value as a mobility aid.
Afger 20 years of intensive research artificial vision has reached the
human beings. of course, it is far away of replacing the natural
system of vision.
Please do not forget, 25 years ago people using a cochlear implant
could identify whether it was a long or a short word. This meant
that they would recognise that a loud speaker is speaking and
could than search for a screen explaining the announcement.
Artifical vision is to be compared to the cochlear implants of 20
years ago. Artificial vision allows the identification of obstacles in
the distance and items in the near with a certainty and can enhance
the independence in mobility and daily living skills of blind people.
Cochlear implants are used today to replace hearing loss of only a
certain group of sounds and not increase e.g. the low sounds. This
would correspond in vision to a central loss of vision, such as
people improve with Stargardt, AMD or DME. It is interesting to see
what the future holds to perfect these systems.
New perspectives
Apart from the classic artificial vision there are two different
research streams that will open completely new perspectives:
- Opto-genetics
- Stem cell research
Opto-genetics uses light sensitive cells from algae that are
incorporated into the ganglion cells of the retina. In the retinae of
people with inherited retinal degenerative diseases such as RP, the
ganglion cells are still there and working. Only the light-sensitive
photoreceptors are gone. Using similar techniques as for gene
therapy, the ganglion cells are infected with melanopsin. The
downside of this approach is that the ganglion cells are slower than
the original photoreceptors and less light sensitive, i.e. they need
much more contrast to be stimulated. This means that the
implanted patient most probably will need to wear spectacles
enhancing contrast. Animal research, also with higher animals, has
been successful. FDA has granted last month permission to carry
out the first clinical trial in humans to a research group at Harvard
University. It is expected that there will be also soon a clinical trial
in Europe carried out by a French team.
Stem cells
Stem cells are the fashionable cells of the last 10 years and the
media promise wonders. However, these are very complex cells and
have to be handled with care. To make it short, there is no stem cell
treatment available to treat vision loss or to restore vision at
present. There are a few clinical trials going on in the USA, Europe
and Japan. In these clinical trials different approaches are tested.
The results are positive, but all researchers underline that there will
be much more research being needed before the stem cells can be
applied safely to humans.