Human Visual System and Retinal Blindness•

• Retina is a light sensitive neural network

• Diseases such as Retinitis Pigmentosa (RP) and Age-related 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 faces

1024 pixels: Reading regular print at regular reading speed

10,000 pixels

Design Implications for Future Implants

Stimulus Threshold Electrode Size

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

optimizationSystem 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.

 

Implantation of LLNL device #4

Postoperative 1st month OCT imaging (horizontal scan)

Postoperative 1st month OCT imaging (vertical scan)

DOE Implants – PDMS Electrode

OCT: Optical Coherence Tomography

Retinal Implant – MEMS Component

microelectronics

electroplated or assembled electrodes

bulk micromachinedelectrode seats

surface micromachinedsprings(polymer) frame

flexible frame for attachment

micromachined electrode array (silicon substrate)

retina

posts for assembly and electrical interconnect

electrodes

flexibleinterconnect

tack

antenna

inner-eyeelectronics

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

9x9 electrode array(test part/ no posts)

array placed in the polymer frame

3D modeland fabricatedpolymer mold

INITIAL WORK ON COATING OF SNL MEMS ELECTRODE STRUCTURES WITH UNCD LAYERS

SEM picture of SNL MEMS Si electrode test structures

SEM pictures of ANL Si tips and posts coated with UNCD film

SEM pictures of SNL MEMS Si electrode test structure coated with UNCD film