•
Human Visual System and
Retinal Blindness
• Retina is a light sensitive
neural network
• Diseases such as Retinitis
Pigmentosa (RP) and Agerelated Macular
Degeneration (AMD)
primarily affect the
photoreceptors, are both
presently incurable, and
render 100,000s blind each
year
Webvision, Kolb, Fernandez, and Nelson, 2003.
Retinal Prosthesis –
Epiretinal vs. Subretinal
Epiretinal



Less disruptive to the
retina.
More flexibility in
component placement
More complex stimulus
algorithms required
Subretinal



In natural position of
photoreceptors
Disruptive to retina
Devices relying on incident
light for power cannot
generate effective stimulus
State of the Art – Retinal Prostheses
• Epiretinal and Subretinal at Investigational Device
Exemption Stage
• Epiretinal - encouraging results, but better technology
required
• Subretinal – No direct evidence demonstrating
functional electrical stimulation, but patients report
subjective improvements in vision
Optobionics
ASRTM
Second Sight Retinal StimulatorTM
Design Requirements for
Higher Resolution Artificial Retina
Unaided Mobility

256-600 pixels: Reading Large Print/Recognizing

1024 pixels: Reading regular print at regular reading

10,000 pixels
faces
speed
Design Implications for
Future Implants

Electrode Size



Stimulus Threshold
Best Case: 6 uA -> 15 micron diameter (irOx, 1 mC/cm2)
Conservative: 100 uA - > 200 micron diameter (Pt, 0.1
mC/cm2)
Device Power

Smaller electrode size will lead to higher impedance, but P=I2R,
so lowering threshold stimulus has large effect on decreasing
power
Image Processing

Eye tracking system, digital zooming, automated
optimization
System layout and packaging

Extraocular component placement is feasible
DOE’s Unique Role in Artificial Retina
Development
DOE LABS have sophisticated design and fabrication
capabilities (ORNL, LLNL, SNL, ANL, LANL)
DOE labs have the ability to work cooperatively with
Universities (USC, UCSC, NCSU) and Industry (Second
Sight)-- CRADA
DOE has the ability to provide sustained support for
high risk, high payoff projects
DOE is used to managing large projects (Genome)
DOE Implants
Polydimehylsiloxane (PDMS) conformable
electrode array from LLNL
•MEMs spring electrode array from SNL
•Ultrananocrystalline diamond (UNCD)
hermetic coating from ANL
•
DOE Implants – PDMS electrode
Goal: To develop a PDMS substrate stimulating
electrode
Progress:
 Four normal sighted dogs were implanted.
Three of them have been followed for 3
months, 2 months and 1 month.
 Multilayer cable PDMS test devices were
received and evaluated.
DOE Implants – PDMS Electrode
OCT: Optical Coherence Tomography
Postoperative 1st month OCT
imaging (horizontal scan)
Implantation of
LLNL device #4
Postoperative 1st month OCT
imaging (vertical scan)
Retinal Implant – MEMS Component
flexible frame for
attachment
(polymer) frame
microelectronics
surface micromachined
springs
posts for
assembly
and electrical
interconnect
antenna
inner-eye
electronics
flexible
interconnect
micromachined electrode
array (silicon substrate)
bulk micromachined
electrode seats
tack
electrodes
retina
electroplated or assembled
electrodes
MEMS electrode array receives signals from an attached antenna and stimulates
the nerve cells that send signals to the bran. Signals originate on a video camera
mounted on a pair of eye glasses.
Bulk Micromachined Components
Bosch etched single crystal silicon electrodes
Polymer frame / test parts
3D model
and fabricated
polymer mold
9x9 electrode array
(test part/ no posts)
array placed in the polymer frame
INITIAL WORK ON COATING OF SNL MEMS
ELECTRODE STRUCTURES WITH UNCD LAYERS
SEM picture of SNL MEMS
Si electrode test structures
SEM pictures of SNL MEMS Si electrode
test structure coated with UNCD film
SEM pictures of ANL Si tips and posts
coated with UNCD film