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Human Visual System and Retinal Blindness

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.

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Human Visual System and Retinal Blindness

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  1. 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.

  2. 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

  3. 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 Second Sight Retinal StimulatorTM Optobionics ASRTM

  4. 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

  5. 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 optimization System layout and packaging • Extraocular component placement is feasible

  6. 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)

  7. DOE Implants • Polydimehylsiloxane (PDMS) conformable electrode array from LLNL • MEMs spring electrode array from SNL • Ultrananocrystalline diamond (UNCD) hermetic coating from ANL

  8. 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.

  9. Postoperative 1st month OCT imaging (horizontal scan) Postoperative 1st month OCT imaging (vertical scan) Implantation of LLNL device #4 DOE Implants – PDMS Electrode OCT: Optical Coherence Tomography

  10. antenna inner-eye electronics flexible interconnect tack electrodes Retinal Implant – MEMS Component posts for assembly and electrical interconnect flexible frame for attachment microelectronics surface micromachined springs (polymer) frame bulk micromachined electrode seats micromachined electrode array (silicon substrate) 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.

  11. Bulk Micromachined Components Bosch etched single crystal silicon electrodes

  12. Polymer frame / test parts 3D model and fabricated polymer mold 9x9 electrode array (test part/ no posts) array placed in the polymer frame

  13. 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

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