1. WELCOME 1

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3. OUTLINE INTRODUCTION NATURAL EYE Basic structure Working ARTIFICIAL EYE ASR chip Implantation of ASR chip Components of artificial eye Video camera in eye glasses Fibre optic element Detector element Coupler WORKING OF ARTIFICIAL EYE RETINAL STIMULATION ADVANTAGES AND DISADVANTAGES CONCLUSION REFERENCES 3

4. INTRODUCTION Twenty five million people worldwide are blind because one layer of cells on their retinas no longer works. By 2020,this figure is expected to double. Using information technology, researches are developing an artificial retina. Their efforts yielding results. For example, with the help of an experimental artificial retina, a man who has been blind for 50 years is now able to see. 4

5. NATURAL EYE An eye is an organ of vision that detects light. Main parts are Cornea, Iris, Retina, Lens, Pupil. The conjunctiva is a clear membrane covering the white of eye. The lens helps to focus light on retina. The optic nerve conducts visual impulses to the brain from the retina. 5

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7. WORKING OF NATURAL EYE The light rays enter the eye through the cornea. Then move through pupil, crystalline lens, vitreous humour and finally fall on the retina. Retina processes and converts incident light to neuron signals using special pigments in rod and cone cells. These neuron signals are transmitted through the optic nerve. 7

8. WORKING…. The neuron signals move through the visual pathway: Optic nerve-optic chiasm-optic tract-optic radiations- Cortex. The neuron signals reach the visual cortex and its radiations for the brain`s processing. The visual cortex interprets the signals as images and along with other parts of brain, interpret the images to extract form, meaning, memory and context of the images 8

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10. ASR CHIP ASR chip is made of silicon and is enclosed in plastic material known as PMMA. The ASR microchip is powered by incident light and does not require the use of external wires or batteries. The microsurgical procedure consists of a standard ophthalmic operation called a vitrectomy and retinotomy, plus the implantation of the chip, itself. 10

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12. IMPLANTATION OF ASR CHIP The surgeon starts by making three tiny incisions in the white part of the subjects eye Through these incisions,the surgeon replaces the vitreous gel in the middle of the eye with saline. Makes an opening in the retina through which fluid is injected: the fluid lifts up a portion of the retina from the back of the eye. Create a small pocket in the subretinal space just wide enough to accommodate the ASR microchip 12

13. The surgeon then slides the implant into the subretinal space Then he introduces air into the middle of the eye to gently push the retina back down over the implant Over a period of one or two weeks,the air bubble is reabsorbed and replaced by fluids created within the eye 13

14. ASR chip in sub retinal space 14

15. COMPONENTS OF ARTIFICIAL EYE Video camera in eye glasses Fiber-optic element Detector element Coupler 15

16. VIDEO CAMERA IN EYE GLASSES Visual signals are captured by a small video camera in the eye glasses of the blind person using a charge coupled (CCD) sensor The CCD sensor digitises the visual image intercepted by the camera The digital representations of the images are then beamed via laser pulses into a microchip and processed through a microcomputer worn on a belt 16

17. CHARGE COUPLED DEVICE(CCD) CCD is an image sensor, consisting of an integrated circuit containing an array of linked, or coupled, capacitors sensitive to light Under the control of an external circuit, each capacitor can transfer its charge to one or other neighbors The photoactive region of the CCD is, an epitaxial layer of silicon It has a doping of p+ (Boron) and is grown upon the substrate material, often p++ 17

18. FIBRE-OPTIC ELEMENT For directing incoming visible light of a particular intensity to detector element A micro lens is placed in front of the fibre-optic element to focus incoming light into the fibre-optic element A coloured filter is placed in front of the micro lens to pass light corresponding to a particular colour to the micro lens 18

19. Consist of a glass core,sourrounded by a glass optical cladding giving an outside dia about 120micrometers The cladding keeps the value of critical angle constant throughout the whole length of the fibre 19

20. DETECTOR ELEMENT The detector used is a micro photodiode. Light of sufficient photon energy strikes the diode, it excites an electron and a positively charged electron hole The micro photodiodes convert the light energy from images into electro chemical impulses that stimulate the remaining functional cells of the retina in patients The detector element is a photodiode which emits an output signal as a function of intensity of incoming signal The output of detector is fed to the coupler 20

21. COUPLER The coupler is used to couple the output of detector to the optic nerve It used a scanning tunnelling microscope (STM) tip The STM tip receives an electrical signal from the photodiode and transmits an electrical signal to the retinal nerves STM tips are basically metal wires that are finely sharpened at one end This end is coupled to the photodiode, while the sharpened end is directed towards the retina for releasing current at specific point on the retina 21

22. WORKING OF ARTIFICIAL EYE Visual signals are captured by a small video camera in the eyeglasses of the blind person using a charge coupled device(CCD) sensor The CCD sensor digitises the visual images intercepted by the camera The digital representations of the images are then beamed via laser pulses into a microchip implanted in the eye and processed through a microcomputer worn on a belt The signals are transmitted to the electrode array in the eye The array stimulates optical nerves, which the carry a signal to the brain 22

23. RETINAL STIMULATION To ways of retinal stimulation They are sub-retinal stimulation and epi-retinal stimulation Sub retinal approach involves the electrical stimulation of inner retina from the sub retinal space by implantation of a semiconductor based micro photodiode array(MPA) into this location. The epiretinal approach involves a semiconductor based device placed above the retina,close to or in contact with the nerve fiber layer retinal ganglion cells. 23

24. SUB-RETINAL VS EPI-RETINAL STIMULATION Fixing a electrode array is easier with sub-retinal stimulation than epiretinal stimulation. Sub retinal stimulation intact optics whereas epiretinal stimulation does not. Sub retinal stimulation is a lot of more electrical power that epiretinal stimulation Sub retinal stimulation can used retinals circuitry. epiretinal stimulation requires the processing of visual information into specific patterns for stimulation of retinal ganglion cells. 24

25. ADVANTAGES ASR microchip can restore eye sight for millions of blind people. If the future artificial retinas can be made from thin films that can shift their molecular configurations on- the-fly, it may be possible to even configure the retinas to look at different parts of the light specific as well. The silicon retina can also be used in cameras for remote monitoring for safety, identification purpose. The researchers have built a prototype that contains 256 pixels, and are working to make a more complete silicon-based system that can be used in autonomous robot and smart sensors. 25

26. DISADVANTAGES There is risk of retinal damage at implantation. The video cameras and complicated image processing software that are used to give machines the ability to see are relatively bulky and expensive. The silicon retina provides information about the edges of image rather than a whole picture. 26

27. CONCLUSION Artificial eye will be a wonderful boon that will restore eyesight for millions of blind people. Obviously, the first users of artificial retina technology will be blind people. Once the resolution of an artificial retina exceeds that of the human eye and it becomes possible to combine it with zoom capability, artificial eye implants will also become attractive for people with perfectly healthy eyes. 27

28. REFERENCES Towards artificial eye a paper presented by Dagnelie G. Massof,Johns Hopkins Univ.Sch.of med., Baltimore, MD appeared in IEEE Spectrum,May 1996,volume 33,issue 5. E-eye: For the blind and beyond Electronics for you magazine, September 2006. Reni Jogi, (2004),Basic Opthalmologyby, Jaypee Publications, Edition 3,New Delhi. The Artificial Silicon Retina(ASR) microchip for the treatment of retinitis Pigmentosaby Alan Y. Chow, MD; Vincent Y.Chow,BS, April 2004. 28