Low Power Artificial Retina By Duha Jabakhanji Content

Low Power Artificial Retina By Duha Jabakhanji

Content ²Introduction: ² Prosthetic Implants ² The Eye ² The retina ² Types of vision implants ² Subretinal Implants: ² Why subretinal implants? ² How it works ² Clinical trials ² Challenges: ² The main issues ² Temperature Variable Supply Voltage ² How it works ² The Project: ² Project Plan ² Time Table

Introduction: Prosthetic Implants ² What to look for in prosthetic implants? ² Stability ² Biocompatibility ² Small and Lightweight ² Non-Intrusive and requiring a simple surgery to implant the device ² Low Power

Introduction: The eye

Introduction: The retina Light

Introduction: Types of vision implants ² Depending on the type of vision impairment, there are different types of implants.

²Retinal Prosthesis Epiretinal prosthesis

Subretinal Prosthesis

²Optic Nerve Prosthesis

Subretinal Implants: Why Subretinal Implants? Advantages: ² More stable due to their location in the retina. Easier to attach. ² No need for extra equipment, it is a stand-alone unit. ² Uses solar power instead of a battery. No need to send the chip power. ² Easy surgery to implant the chip. Patients recover within a day.

Subretinal Implants: Why Subretinal Implants? Disadvantages: ² Applies only to two kinds of blindness: retinitis pigmentosa and age-related macular degeneration. ² Remote area in the subretinal space.

Subretinal Implants: How it works Retinitis pigmentosa and age-related macular degeneration degrades the rods and cones, but spares the remainder of the retina.

Subretinal Implants: How it works ² If the bipolar cells and horizontal cells are replaced, then edge detection circuitry is needed. ² Other wise, only a circuit that converts the current from the photo diode into pulses is needed. ² The frequency of the pulses depends on the intensity of the light. ² There are many different circuits to implement the chip.

Subretinal Implants: How it works M. Mazza, P. Renaud, D. C. Bertrand, and A. M. Ionescu, “CMOS Pixels for Subretinal Implantable Prothesis”

Subretinal Implants: Clinical Trials ² ² ² Subretinal implants have been tested on animals. Recently they have been implanted in humans. Degradation in the retina has been observed in patients. Reasons are not fully understood. Possible reason is the blocking nutrients from reaching the retina. ² Laser holes have to be drilled to allow the flow of nutrients. ² No patients have shown any rejection, infection, erosion, inflammation or retinal detachment. ² Its long-term effects have yet to be tested. ² In some cases the artificial retina has failed, cause unknown.

Challenges: The main issues ² ² ² Size is critical, the smaller the circuit the better. 200 -pixel matrix is needed for basic orientation. 650 -pixel matrix is needed for ordinary script reading. Low power consumption is a must. Due to its remote location on the eye, methods of delivering power are difficult. ² Solar arrays power is limited. ² Location of the subretinal implant makes heat dissipation difficult. ² It also comes in contact with retinal cells, making heat damage an issue.

Challenges: Temperature Variable Supply voltage (TVS) ² A temperature variable supply voltage is suggested to lower power. ² The circuit will detect the temperature of the chip and lower its voltage supply accordingly. ² This will lower power consumption and heat dissipation. ² It will consequently lower the temperature of the chip. ² P=Pdy+Pst+Psc ² Pdy= CVdd 2 f ² Pst=Vdd. Isub ² Isub=I 0 Exp{Vthq/ k. T-1} ² Cox is oxide capacitance and CD 0 is depletion capacitance. ² 0 is the low field mobility, K the Boltzman constant, and Weff and Leff are the effective width and length respectively.

Challenges: How Temperature Variable Supply voltage (TVS) works G. Ono, M. Miyazaki, H. Tanaka, N. Ohkubo, and T. Kawahara, “Temperature referenced supply voltage and forward-body-bias control (TSFC) architecture for minimum power consumption [ubiquitous computing processors]”

Challenges: How Temperature Variable Supply voltage (TVS) works Solar Panel Control Circuit A/D converter Temperature Sensor VDD

Project Plan ² O. 13 Technology will be used. ² Pixel array will be designed. S ² Solar array will not be ol ar implemented. P ² TVS circuit will be designed. an el ² Both circuits will be combined. ² An environment similar to the subretinal space is to be simulated. Solar Panel T VS Pixel Array Solar Panel S ol ar P a n el

Time table Feb-16 Mar-12 Mar-28 Mar-31 April-20 (two weeks after the final) Design of the chip (putting the circuits together) Implementation and testing (using Cadence) Second Presentation Final report

References [1] M. Mazza, P. Renaud, D. C. Bertrand, and A. M. Ionescu, “CMOS Pixels for Subretinal Implantable Prothesis”, IEEE Sensors Journal, Vol. 5, No. 1, February 2005. [2] C. Y. Wu, F. Cheng, C. T. Chiang, and P. K. Lin, “ A Low-Power implantable pseudo-BJT-based silicon retina with solar cells for artificial retinal prosthesis”, Circuits and Systems, 2004. ISCAS '04. Proceedings of the 2004 International Symposium on, Volume: 4 , 23 -26 May 2004 [3] K. Shakeri, and J. D. Meindl, “Temperature Variable Supply Voltage for Power Reduction”, VLSI, 2002. Proceedings. IEEE Computer Society Annual Symposium on, 25 -26 April 2002, Pages: 64 – 67 [4] G. Ono, M. Miyazaki, H. Tanaka, N. Ohkubo, and T. Kawahara, “Temperature referenced supply voltage and forward-body-bias control (TSFC) architecture for minimum power consumption [ubiquitous computing processors]” Solid-State Circuits Conference, 2004. ESSCIRC 2004. Proceeding of the 30 th European, 21 -23 Sept. 2004, Pages: 391 – 394

[5] E. Marggalit et al. “Retinal Prosthesis for the Blind”, Opthamology. Survey of, Vol. 47, No. 4, July-August 2002 [6] E. Funatsu, Y. Nitta, Y. Miyake, T. Toyoda, J. Ohta, and K. Kyuma, “ An Artificial Retina Chip with Current-Mode Focal Place Image Processing Functions” Electron Devices, IEE Transaction on, Vol. 44, No. 10, October 1997 [7] F. Paillet, D. Mercier, T. M. Bernard, and E. Senn, “ Low Power Issues in a Digital Programmable Artificial Retina” Low-Power Design, 1999. Proceedings. IEEE Alessandro Volta Memorial Workshop on, 4 -5 March 1999 Pages: 153 - 161 [8] M. S. Humayum et al. “Pattern electrical stimulation of the human retina”, Vision research 39, 1999 pages: 2569 -2576 [9] C. Y. Wu, L. J. Lin, K. H. Huang, “ A new light-activated CMOS retinalpulse generation circuit without external power supple for artificial retinal prosthesis” Electronics, Circuits and Systems, 2001. ICECS 2001. The 8 th IEEE International Conference on, Volume: 2 , 2 -5 Sept. 2001 Pages: 619 - 622 vol. 2