Current and Upcoming
Now, let’s consider 2 treatments where
few or no photoreceptor cells remain
Possible treatments here would include:
• Donor Photoreceptor Cell and Stem
• The use of Electronic Prosthetic
Photoreceptor Cell Transplantation
• The idea of replacing dead photoreceptor
cells with new, donor photoreceptors by
transplantation has long been worked on.
• There is a small human Clinical Trial on
transplantation of photoreceptor cells being
conducted by Dr. Norman Radtke in the USA.
• It has proven the relatively safety of the
technique. BUT, unfortunately, there has not
been much good news from the study as to
improvement in vision in the patients.
Thus, with only very modest positive results
from both animal and human studies, it is
difficult to see how this will be a viable
treatment in the future.
Transplantation: Stem Cells
An exciting new area of research is in the
study of Stem Cell transplantation.
• Stem cells are cells that have the potential of
multiplying and developing into almost any
type of cell in the body.
• Thus, theoretically, stem cells could be
transplanted into the retinal space where
photoreceptor cells have died and could
develop and replace them.
• However, proper and complex biological
signals have to be given to the stem cells
such that they develop into mature,
functional photoreceptor cells – instead of
other cell types.
A Stem Cell Clinical Trial?
• There are some reports that a clinical trial
using stem cells on RP patients has been
stopped in the USA. However, the company
has not confirmed that stem cells were
actually being used.
• There are also reports of commercial stem
cell therapy in some other countries but
these are not well documented as to
scientific safety and efficacy.
• Much more work needs to be done on stem
cells before they can be used as an RD
Electronic Prosthetic Devices
for Sight Restoration
These fall into 2 categories:
1) Brain (cortical) electronic implants
2) Retinal implants – in front or behind
For the retinal implants, there are many
different designs and surgical
approaches from groups around the
Brain Prosthetic Devices
Three main groups of investigators have worked
or are working on brain prosthetic devices that
will have the potential to bypass the eye
• One group has prematurely done human
implants with poor results.
• A second group continues to do mainly basic
• The third group is doing excellent work in
monkey and is planning a human clinical trial.
How Does the Retinal Prosthesis
• The device uses electrical signals to
bypass defective or dead photoreceptors
and stimulate remaining viable, non-
photoreceptor cells of the retina.
• Images comes from an external video
camera worn behind the patient’s glasses.
• The images are transmitted through a
computer to electrodes (called an array)
attached to the retina to reproduce the
visual image in the brain.
Retinal Prosthesis Trials
Groups in many countries are developing
There are 4 groups around the world that have
implanted human subjects with retinal
prosthetic devices of different design.
• Optobionics Co. (Chicago, IL) – poor design
such that it does not function well or at all.
• 2 excellent German companies – early stages
of human testing – e.g., Retina Implant AG.
• Second Sight (Sylmar, CA) – with Dr.
Humayun, has already implanted 6 subjects
in a Phase 1 study and now over 10 subjects
in a Phase 2 Clinical Trial that recently
Phase 1 Patient Update
Chronic studies on human implants have
been done on an early electrode device
with 16 electrodes -- from 2/02.
Six patients were implanted. There were
NO device failures.
All subjects saw discrete visual images
(called phosphenes) and could perform
visual spatial and motion tasks.
Mobility (walking and navigation) has been
The remaining 5 patients use the device at
Retinal Prostheses – The Future
• Several clinical trials have been started. If
successful, commercial models should soon
become available for implant.
• Designs are improving to increase the
number of electrodes touching the retina.
• Theoretically, a design with about 1,000
electrodes is needed to give reading ability
and face recognition.
• The prosthetic device may be the best hope
for restoring sight to severely affected RP
and dry AMD patients.
In Conclusion for RP….
Several Clinical Trials are in progress. Proof of
Principle for several other types of therapies
has been established.
• For example, Gene Therapy work on a dog
model of RP-LCA shows not only sight
restoration but a long term, positive effect.
• Other basic work in the fields of gene
therapy, stem cell research, pharmaceutical
therapy, nutrition and electronic implants
show promise in current and future Clinical