Bionic lens report


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Bionic lens report

  1. 1. Bionic Eye: A Look into Current Research and Future ProspectsChapter 1 INTRODUCTION Technology has done wonders for the mankind. We have seen prosthetics thathelped overcome handicaps. Bio medical engineers play a vital role in shaping the courseof these prosthetics. Now it is the turn of Artificial Vision through Bionic Eyes. Chips are designed specifically to imitate the characteristics of the damagedretina, and the cones and rods of the organ of sight are implanted with a microsurgery.Whether it be Bio medical, Computer, Electrical, or Mechanical Engineers – all of themhave a role to play in the personification of Bionic Eyes. There is hope for the blind in theform of Bionic Eyes. This technology can add life to their vision less eyes! Sooner or later, this shall create a revolution in the field of medicine. It isimportant to know few facts about the organ of sight i.e. the Eye before we proceedtowards the technicalities involved.1.1 The Eye Our ability to see is the result of a process similar to that of a camera. This isshown in fig 1.1. In a camera, light passes through a series of lenses that focus imagesonto film or an imaging chip. The eye performs a similar function in that light passes Fig 1.1: Eye-camera similarity.Dept. of IT, GSSSIETW, Mysore 1
  2. 2. Bionic Eye: A Look into Current Research and Future Prospectsthrough the cornea and crystalline lens, which together focus images onto the retina—thelayer of light sensing cells that lines the back of the eye. The retina represents the film inour camera. It captures the image and sends it to the brain to be developed. Once stimulated by light, the cells within the retina process the images byconverting their analog light signals into digital electro-chemical pulses that are sent viathe optic nerve to the brain. A disruption or malfunction of any of these processes canresult in loss of vision.1.2 How are We Able to See? For vision to occur, 2 conditions need to be met:a) An image must be formed on the retina to stimulate its receptors (rods and cones).b) Resulting nerve impulses must be conducted to the visual areas of the cerebral cortexfor interpretation. Fig 1.2: The EyeFour processes focus light rays, so that they form a clear image on the retina:1. Refraction of light rays2. Accommodation of the lens3. Constriction of the pupil4. Convergence of the eyesDept. of IT, GSSSIETW, Mysore 2
  3. 3. Bionic Eye: A Look into Current Research and Future Prospects1.3 Retina The retina is the innermost layer of the wall of the eyeball. Fig 1.3 shows thestructure of Retina and fig 1.4 shows the Eye with Retina. Millions of light sensitive cellsthere absorb light rays and convert them to electrical signals. Light first enters the optic(or nerve) fiber layer and the ganglion cell layer, under which most of the nourishingblood vessels of the retina are located. This is where the nerves begin, picking up theimpulses from the retina and transmitting them to the brain. The light is received by photoreceptor cells called rods (responsible for peripheraland dim light vision) and cones (providing central, bright light, fine detail, and colourvision). The photoreceptors convert light into nerve impulses, which are then processedby the retina and sent through nerve fibers to the brain. The nerve fibers exit the eyeball atthe optic disk and reach the brain through the optic nerve. Directly beneath thephotoreceptor cells is a single layer of retinal pigment epithelium (RPE) cells, whichnourish the photoreceptors. These cells are fed by the blood vessels in the choroids. LIGHT Fig 1.3: RetinaDept. of IT, GSSSIETW, Mysore 3
  4. 4. Bionic Eye: A Look into Current Research and Future Prospects Fig 1.4: The retinal layers1.4 Retinal Disease There are two important types of retinal degenerative disease:a) Retinitis pigmentosa (RP), andb) Age-related macular degeneration (AMD)They are detailed below. Retinitis Pigmentosa (RP) is a general term for a number of diseases thatpredominately affect the photoreceptor layer or ―light sensing‖ cells of the retina. Thesediseases are usually hereditary and affect individuals earlier in life. Injury to thephotoreceptor cell layer, in particular, reduces the retina’s ability to sense an initial lightsignal. Despite this damage, however, the remainder of the retinal processing cells inother layers usually continues to function. RP affects the mid-peripheral vision first andsometimes progresses to affect the far-periphery and the central areas of vision. Thenarrowing of the field of vision into ―tunnel vision‖ can sometimes result in completeblindness. Age-related Macular Degeneration (AMD) refers to a degenerative conditionthat occurs most frequently in the elderly. AMD is a disease that progressively decreasesthe function of specific cellular layers of the retina’s macula. The affected areas withinthe macula are the outer retina and inner retina photoreceptor layer. As for maculardegeneration, it is also genetically related, it degenerates cones in macula region, causingdamage to central vision but spares peripheral retina, which affects their ability to readDept. of IT, GSSSIETW, Mysore 4
  5. 5. Bionic Eye: A Look into Current Research and Future Prospectsand perform visually demanding tasks. Although macular degeneration is associated withaging, the exact cause is still unknown. Together, AMD and RP affect at least 30 million people in the world. They are themost common causes of untreatable blindness in developed countries and, currently, thereis no effective means of restoring vision.Dept. of IT, GSSSIETW, Mysore 5
  6. 6. Bionic Eye: A Look into Current Research and Future ProspectsChapter 2 NEED FOR BIONIC EYE The absence of effective therapeutic remedies for Retinitis pigmentosa (RP) andAge-related macular degeneration (AMD) has motivated the development ofexperimental strategies to restore some degree of visual function to affected patients.Because the remaining retinal layers are anatomically spared, several approaches havebeen designed to artificially activate this residual retina and thereby the visual system. It has been shown that electric stimulation of retinal neurons can produceperception of light in patients suffering from retinal degeneration. Using this property wecan make use of the functional cells to retain the vision with the help of electronic devicesthat assist this cells in performing the task of vision, we can make these lakhs of peopleget back their vision at least partially. A design of an optoelectronic retinal prosthesissystem that can stimulate the retina with resolution corresponding to a visual activity of20/80—sharp enough to orient yourself toward objects, recognize faces, read large fonts,watch TV and, perhaps most important, lead an independent life. The researchers hopetheir device may someday bring artificial vision to those blind due to retinal degeneration.2.1 What is a Bionic Eye? A visual prosthesis often referred to as a bionic eye or retinal implant, is anexperimental visual device intended to restore functional vision. A visual prosthetic orbionic eye is a form of neural prosthesis intended to partially restore lost vision oramplify existing vision. It usually takes the form of an externally-worn camera that isattached to a stimulator on the retina, optic nerve, or in the visual cortex, in order toproduce perceptions in the visual cortex. Bionic eye restores the vision lost due to damageof retinal cells. A Bionic Eye is a device, which acts as an artificial eye. It is a broad term for theentire electronics system consisting of the image sensors, processors, radio transmitters &receivers, and the retinal chip. The device is a circle about the size of a five-cent piece,inserted into the eye where the retina sits. It is a silicon chip which decodes the radiosignals and delivers the stimulations. When these electrodes are stimulated they sendmessages to the retinal ganglion cells through small wires and then to the optic nerve toDept. of IT, GSSSIETW, Mysore 6
  7. 7. Bionic Eye: A Look into Current Research and Future Prospectsthe brain, which is able to perceive patterns of light and dark spots corresponding towhich electrodes have been stimulated. The device receives signals from a pair of glassesworn by the patient, which are fitted with a camera. The camera feeds the visual information into a separate image-processing unit,which makes sense of the image by extracting certain features. The unit then breaksdown the image into pixels and sends the information, one pixel at a time, to the siliconchip, which then reconstructs the image. Data is broadcasted into the body using radiowaves. Its like a radio station that only has a range of 25 millimeters. Currently the technology is only able to transmit a 10 x 10 pixel. Participants mustbe profoundly blind to be eligible — those with even partial vision are excluded due tothe potential risk of visual damage. The most recent version of the implant features an array of 60 pixels, allowingusers to distinguish between light and dark, and see certain distinct objects. The ultimategoal, according to the research team, is to allow for reading and face recognition byincreasing the number of pixels to 1,000.2.2 The Bionic Eye System Visual prosthetics can be broken into three major groups. First, there are thedevices that use either ultrasonic sound or a camera to sample the environment ahead ofan individual and render the results into either a series of sounds or a tactile display. Fromthis the person is supposed to be able to discern the shape and proximity of objects intheir path. The second major form is retina enhancers. These machines supplement functionsof the retina by stimulating the retina with electrical signals which in turn causes theretina to send the results through the optic nerve to the brain. The third major category of visual prosthetic is a digital camera that samples animage and stimulates the brain with electrical signals--either by penetrating into orplacing electrodes on the surface of the visual cortex.Dept. of IT, GSSSIETW, Mysore 7
  8. 8. Bionic Eye: A Look into Current Research and Future Prospects2.3 Retinal Implant Systems Now, a company called Second Sight has received FDA approval to begin U.S.trials of a retinal implant system that gives blind people a limited degree of vision.Second Sight’s first generation Argus 16 implant consists of a 16 electrode array and arelatively large implanted receiver implanted behind the ear. The second generationArgus II is designed with a 60 electrode array and a much smaller receiver that isimplanted around the eye. It (Argus II) is an array of electrodes that is surgically implanted onto the retina –the layer of specialized cells that normally respond to light found at the back of the eye.This array of electrodes is able to send signals to the brain that the person’s biologicalretina is unable to send. Of course, the electrode array is not very useful unless it isreceiving visual data to send to the brain. To solve this problem the patient is fitted with apair of glasses that contain a tiny video camera that continuously records footage of whatis in front of the patient. This video signal is sent wirelessly to a wearable computer thatfirst filters and processes the video signal and then feeds this formatted data to theelectrode array. A picture of the entire setup can be shown in fig 2.1. Fig 2.1: Argus IIDept. of IT, GSSSIETW, Mysore 8
  9. 9. Bionic Eye: A Look into Current Research and Future Prospects The Argus II Retinal Prosthesis System can provide sight -- the detection oflight -- to people who have gone blind from degenerative eye diseases like maculardegeneration and retinitis pigmentosa. Both diseases damage the eyes photoreceptors,the cells at the back of the retina that perceive light patterns and pass them on to the brainin the form of nerve impulses, where the impulse patterns are then interpreted as images.The Argus II system takes the place of these photoreceptors. The second incarnation of Second Sights retinal prosthesis consists of five mainparts:a) A digital camera thats built into a pair of glasses. It captures images in real time andsends images to a microchip.b) A video-processing microchip thats built into a handheld unit. It processes imagesinto electrical pulses representing patterns of light and dark and sends the pulses to aradio transmitter in the glasses.c) A radio transmitter that wirelessly transmits pulses to a receiver implanted above theear or under the eye.d) A radio receiver that sends pulses to the retinal implant by a hair-thin implanted wire.e) A retinal implant with an array of 60 electrodes on a chip measuring 1 mm by 1 mm. The entire system runs on a battery pack that is housed with the video processingunit. When the camera captures an image -- of, say, a tree – the image is in the form oflight and dark pixels. It sends this image to the video processor, which converts the tree-shaped pattern of pixels into a series of electrical pulses that represent "light" and "dark". The processor sends these pulses to a radio transmitter on the glasses, which thentransmits the pulses in radio form to a receiver implanted underneath the subjects skin.The receiver is directly connected via a wire to the electrode array implanted at the backof the eye, and it sends the pulses down the wire. When the pulses reach the retinalimplant, they excite the electrode array. The array acts as the artificial equivalent of theretinas photoreceptors. The electrodes are stimulated in accordance with the encodedpattern of light and dark that represents the tree, as the retinas photoreceptors would be ifthey were working (except that the pattern wouldnt be digitally encoded). The electrical signals generated by the stimulated electrodes then travel as neuralsignals to the visual center of the brain by way of the normal pathways used by healthyDept. of IT, GSSSIETW, Mysore 9
  10. 10. Bionic Eye: A Look into Current Research and Future Prospectseyes -- the optic nerves. In macular degeneration and retinitis pigmentosa, the opticalneural pathways arent damaged. The brain, in turn, interprets these signals as a tree andtells the subject, "Youre seeing a tree."2.4 Working The working of Retinal implant system is shown in fig 2.2. Normal vision beginswhen light enters and moves through the eye to strike specialized photoreceptor (light-receiving) cells in the retina called rods and cones. These cells convert light signals toelectric impulses that are sent to the optic nerve and the brain. Retinal diseases like age-related macular degeneration and retinitis pigmentosa destroy vision by annihilating thesecells. With the artificial retina device, a miniature camera mounted in eyeglassescaptures images and wirelessly sends the information to a microprocessor (worn on abelt) that converts the data to an electronic signal and transmits it to a receiver on the eye.The receiver sends the signals through a tiny, thin cable to the microelectrode array,stimulating it to emit pulses. The artificial retina device thus bypasses defunctphotoreceptor cells and transmits electrical signals directly to the retina’s remainingviable cells. The pulses travel to the optic nerve and, ultimately, to the brain, whichperceives patterns of light and dark spots corresponding to the electrodes stimulated. Patients learn to interpret these visual patterns. It takes some training for subjectsto actually see a tree. At first, they see mostly light and dark spots. But after a while, theylearn to interpret what the brain is showing them, and they eventually perceive thatpattern of light and dark as a tree. Researchers are already planning a third version that has a1000 electrodes on theretinal implant, which they believe could allow for reading, facial recognition capabilitiesetc.1: Camera on glasses views image2: Signals are sent to hand-held device3: Processed information is sent back to glasses and wirelessly transmitted to receiver under surface of eye4: Receiver sends information to electrodes in retinal implantDept. of IT, GSSSIETW, Mysore 10
  11. 11. Bionic Eye: A Look into Current Research and Future Prospects5: Electrodes stimulate retina to send information to brain. Fig 2.2: Working of Retinal Implant SystemDept. of IT, GSSSIETW, Mysore 11
  12. 12. Bionic Eye: A Look into Current Research and Future ProspectsChapter 3 OCULAR IMPLANT Ocular implants are those which are placed inside the retina. It aims at theelectrical excitation of two dimensional layers of neurons within partly degeneratedretinas for restoring vision in blind people. The implantation can be done using standardtechniques from ophthalmic surgery. Neural signals farther down the pathway areprocessed and modified in ways not really understood therefore, the earlier the electronicinput is fed into the nerves the better. There are two types of ocular implants: Epi-retinalimplants and Subretinal implants. The ocular implantation is shown in Fig 2.3.Fig 3.1: Section of the eye showing the retina and its layers. In conditions such as retinitis pigmentosa and macular degeneration, the light sensing rod and cone cells ("photoreceptors") no longer function. A retinal prosthesis can be placed either on the retinal surface ("epi-retinal") or below the retina in the area of damaged photoreceptors ("sub-retinal") to try to stimulate the remaining cells.Dept. of IT, GSSSIETW, Mysore 12
  13. 13. Bionic Eye: A Look into Current Research and Future Prospects3.1 Epi-Retinal Implants The ―Epiretinal‖ approach involves a semiconductor-based device placed abovethe retina, close to or in contact with the nerve fiber layer retinal ganglion cells. Theinformation in this approach must be captured by a camera system before transmittingdata and energy to the implant. In the EPI-RET approach scientists had developed a micro contact array which ismounted onto the retinal surface to stimulate retinal ganglion cells. A tiny video camera ismounted on eyeglasses and it sends images via radio waves to the chip. The actual visualworld is captured by a highly miniaturized CMOS camera embedded into regularspectacles. The camera signal is analyzed and processed using receptive field algorithmsto calculate electric pulse trains which are necessary to adequately stimulate ganglioncells in the retina. This signal together with the energy supply is transmitted wireless into a devicewhich is implanted into the eye of the blind subject. The implant consists of a receiver fordata and energy, a decoder and array microelectrodes placed on the inner surface of theretina. This micro chip will stimulate viable retinal cells. Electrodes on microchip willthen create a pixel of light on the retina, which can be sent to the brain for processing. The main advantage of this is that it consists of only a simple spectacle frame withcamera and external electronics which communicates wirelessly with microchipimplanted on retina programmed with stimulation pattern. Fig 3.2: Block diagram of the EPI-RET SystemDept. of IT, GSSSIETW, Mysore 13
  14. 14. Bionic Eye: A Look into Current Research and Future ProspectsThe issues involved in the design of the retinal encoder are:a) Chip Developmentb) Biocompatibilityc) RF Telemetry and Power Systemsa) Chip Development:Encoder Epi Retinal The design of an epiretinal encoder is more complicated than the sub retinalencoder, because it has to feed the ganglion cells. Here, a retina encoder (RE) outside theeye replaces the information processing of the retina. A retina stimulator (RS), implantedadjacent to the retinal ganglion cell layer at the retinal output, contacts a sufficientnumber of retinal ganglion cells/fibers for electrical stimulation. A wireless (RadioFrequency) signal and energy transmission system provides the communication betweenRE and RS. The RE, then, maps visual patterns onto impulse sequences for a number ofcontacted ganglion cells by means of adaptive dynamic spatial filters. This is done by adigital signal processor, which, handles the incoming light stimuli with the masterprocessor, implements various adaptive, antagonistic, receptive field filters with the otherfour parallel processors, and generates asynchronous pulse trains for each simulatedganglion cell output individually. These spatial filters as biology-inspired neural networkscan be tuned to various spatial and temporal receptive field properties of ganglion cellsin the primate retina.b) Biocompatibility: The material used for the chips and stimulating electrodes should satisfy a varietyof criteria’s. They must be corrosion-proof, i.e. bio stable.  The electrodes must establish a good contact to the nerve cells within fluids, so that the stimulating electric current can pass from the photo elements into the tissue.  It must be possible to manufacture these materials with micro technical methods.  They must be biologically compatible with the nervous system.Dept. of IT, GSSSIETW, Mysore 14
  15. 15. Bionic Eye: A Look into Current Research and Future Prospectsc) RF Telemetry: In case of the epiretinal encoder, a wireless RF telemetry system acts as a channelbetween the Retinal Encoder and the retinal stimulator. Standard semiconductortechnology is used to fabricate a power and signum receiving chip, which drives currentthrough an electrode array and stimulate the retinal neurons. The intraocular transceiverprocessing unit is separated from the stimulator in order to take into account the heatdissipation of the rectification and power transfer processes. Care is taken to avoid directcontact of heat dissipating devices with the retina.3.2 Sub Retinal Implants Fig 3.3: Sub retinal Implant The ―Sub retinal‖ approach involves the electrical stimulation of the inner retinafrom the sub retinal space by implantation of a semiconductor-based micro photodiodearray (MPA) into this location. The concept of the sub retinal approach is that electricalcharge generated by the MPA in response to a light stimulus may be used to artificiallyalter the membrane potential of neurons in the outer retina or remnants of this structureand thereby activate the visual system. Because the implant is designed to stimulate theretina at an early stage of the visual system, this approach would theoretically allow thenormal processing networks of the retina to transmit this signal centrally. In Retinitis pigmentosa disease, the retinal pigment epithelial cells (RPE) begin todie out and the person starts loosing the vision gradually. Since the function of the retinato transduce light into biological signal is weakened, it causes blindness. SubretinalDept. of IT, GSSSIETW, Mysore 15
  16. 16. Bionic Eye: A Look into Current Research and Future Prospectsimplant is used to substitute the lost RPE cells with the ones of artificial basis to restorethe vision. In this implant, a microphotodiode array (MPD), a silicon micromanufactureddevice, or semiconductor microphotodiode array (SMA) is used. This piece of equipmentis placed behind the retina between the sclera and the bipolar cells. The incident light istransformed into electrical potentials that excite the bipolar cells to form an imagesensation. The arrays can be manufactured by various silicon manufacturing procedures.MPD arrays are manufactured consistently with measurements of each stimulating unit as20 μm X 20 μm, and adjacent units separated as 10 μm. The elements are produced to beresponsive to light corresponding to the visible spectrum (400-700 nm). Severalthousands of the devices can be placed on a single structure of diameter of 3 mm,thickness of 100 μm and with a density same as the replacing RPE cells. These deviceshave demonstrated the same electrophysiological behaviours as the healthy RPE cells. The MPDA has to be very thin and flexible enough in order to be able to fit to thecurvature of the eye ball. Figure below shows an example of such an ultra thin MPDAhaving a thickness of 1.5 micron, together with titanium substrate and silicon nitridepassivation. Fig 3.4: Ultra thin microphotodiode arrayDept. of IT, GSSSIETW, Mysore 16
  17. 17. Bionic Eye: A Look into Current Research and Future Prospects In Subretinal implant, the light-sensitive microphotodiodes with microelectrodesof gold and titanium nitride set in arrays is implanted in the subretinal space. The visiblelight coming from different directions is transformed into small currents by themicrophotodiodes at each of hundreds of microelectrodes. These currents are then passedto the retinal network by neurons. The middle and inner retina captures current and thenprocesses the part of vision. There are many benefits of using the subretinal prostheses.Such as, the MPD directly replaces the lost or degenerated RPE cells; the retina’sremaining network is still capable of processing electrical signals; ease of fixing the highdensity MPDA in the subretinal position; no need of any external camera or externalimage processing equipment; and eye movement to locate the objects is not restricted. There are some of the limitations to the subretinal implants as well. The singleMPD is not enough to stimulate enough current. So a subretinal implant is supported byan external energy source, such as transpupillary infrared illumination of receivers closeto the chip or electromagnetic transfer, is currently under progress. Some of the additionaldevelopments in this process are movement to flexible substrates to hold the subtle natureof the retina and to decrease the light intensity. Fig 3.5: Shows the major difference between epi-retinal &sub retinal approachDept. of IT, GSSSIETW, Mysore 17
  18. 18. Bionic Eye: A Look into Current Research and Future Prospects Now, a German firm dubbed Retina Implant has scored a big win for the subretinal solution with a three-millimeter, 1,500 pixel microchip that gives patients a 12degree field of view.In general,  Epiretinal Approach involves a semiconductor based device positioned on the surface of the retina to try to simulate the remaining overlying cells.  Subretinal Approach involves implanting the ASR chip behind the retina to simulate the remaining viable cells.Dept. of IT, GSSSIETW, Mysore 18
  19. 19. Bionic Eye: A Look into Current Research and Future ProspectsChapter 4 MULTIPLE UNIT ARTIFICIAL RETINA CHIPSET (MARC) The other revolutionary bio electronic eye is the MARC; this uses a CCD camerainput and a laser beam or RF to transmit the image into the chip present in the retina.Using this, a resolution of 100 pixels is achieved by using a 10x10 array. It consists of aplatinum or rubber silicon electrode array placed inside the eye to stimulate the cells. Fig 4.1: The MARC System The schematic of the components of the MARC shown in fig 4.1, consists of asecondary receiving coil mounted in close proximity to the cornea, a power and signaltransceiver and processing chip, a stimulation-current driver, and a proposed electrodearray fabricated on a material such as silicone rubber thin silicon or polyimide withribbon cables connecting the devices. The stimulating electrode array is mounted on the retina while the power andsignal transceiver is mounted in close proximity to the cornea. An external miniature low-power CMOS camera worn in an eyeglass frame will capture an image and transfer thevisual information and power to the intraocular components via RF telemetry. Theintraocular prosthesis will decode the signal and electrically stimulate the retinal neuronsDept. of IT, GSSSIETW, Mysore 19
  20. 20. Bionic Eye: A Look into Current Research and Future Prospectsthrough the electrodes in a manner that corresponds to the image acquired by the CMOSCamera. Fig 4.2: A 5x5 platinum electrode array for retinal stimulation fabricated on silicone rubber and used by doctors at JHU4.1 Working The MARC system, pictured in the fig 4.3 will operate in the following manner.An external camera will acquire an image, whereupon it will be encoded into data streamwhich will be transmitted via RF telemetry to an intraocular transceiver. A data signalwill be transmitted by modulating the amplitude of a higher frequency carrier signal. Thesignal will be rectified and filtered, and the MARC will be capable of extracting power,data, and a clock signal. The subsequently derived image will then be stimulated upon thepatient’s retina.4.1 (a) MARC System Block DiagramOutside Eye: The video input to the marc system block is given through a CCD camera. Thisimage is further processed using a PDA sized image processor & to transmit it, we dopulse width modulation in first stage and then ASK modulation is done. This signal isfurther amplified using a class E power amplifier and transmitted using RF telemetrycoils.Inside Eye: The signal received from the RF telemetry coils is power recovered and then thesesignal is ASK demodulated and the data and clock is recovered from this signals andDept. of IT, GSSSIETW, Mysore 20
  21. 21. Bionic Eye: A Look into Current Research and Future Prospectsthese signal are sent to the configuration and control block of the chip which from itsinput decode what information has to be sent to each of the electrodes and sends them thisdata. And the electrodes in turn stimulate the cells in the eye so as to send this stimulationto the brain through optic nerve and help brain in visualizing the image and while thisprocess is going on the status of each electrode is sent to the marc diagnostics chipoutside the eye. Fig 4.3: Block Diagram of MARC System4.1 (b) Block Diagram of Image Acquisition System The image acquisition system consists of a CMOS digital camera which acquiresimages and sends it to the Analog to Digital Converter. It converts this analog input to Fig 4.4: Block Diagram of Image Acquisition SystemDept. of IT, GSSSIETW, Mysore 21
  22. 22. Bionic Eye: A Look into Current Research and Future Prospectsdigital data. This data is first sent into a video buffer where it is processed, the images arecolor mapped and these processed images are sent through RS232 interface. This serialdata is then sent to the electrodes or testing monitor through a RF circuit or laser beam.4.2 Advantages of the MARC System  Compact Size – 6x6 mm  Diagnostic Capability  Reduction of stress upon retina  Heat dissipation problems are kept to a minimumDept. of IT, GSSSIETW, Mysore 22
  23. 23. Bionic Eye: A Look into Current Research and Future ProspectsChapter 5 APPLICATIONS PROPOSED  Adding displays directly onto the lenses, visible to the wearers but no one else, could project critical information like routes, weather, vehicle status onto windshields for drivers or pilots or superimpose computer images onto real-world objects for training exercises.  Besides visual enhancement, noninvasive monitoring of the wearer’s biomarkers and health indicators could be extremely useful. Several simple sensors that can detect the concentration of a molecule, such as glucose have been built onto lenses. These would let diabetic wearers keep tabs on blood-sugar levels without needing to prick a finger.  Lenses remain in contact, through fluids, with the interior of the body and an appropriately configured contact lens could monitor cholesterol, sodium, and potassium levels, to name a few potential targets. Coupled with a wireless data transmitter, the lens could relay information to medics or nurses instantly, without needles or laboratory chemistry.  Bionic lenses could aid people with impaired hearing.  Future versions, the scientists believe, they could serve as a flexible plastic platform for applications such as surfing the Internet on a virtual screen, immersing gamers in virtual worlds.Dept. of IT, GSSSIETW, Mysore 23
  24. 24. Bionic Eye: A Look into Current Research and Future ProspectsChapter 6 CHALLENGES  Biology imposes limitations, such as the needs for a system that will not heat cells by more than 1 degree Celsius and for electrochemical interfaces that arent corrosive.  There are many very many obstacles to be overcome before Bionic Eyes become a success story. Our eyes are perhaps the most sensitive of all organs in the human body. A nano-sized irritant can create havoc in the eye.  There are 120 million rods and 6 million cones in the retina of every healthy human eye. Creating an artificial replacement for these is no easy task.  Si based photo detectors have been tried in earlier attempts. But Si is toxic to the human body and reacts unfavorably with fluids in the eye.  There are many doubts as to how the brain will react to foreign signals generated by artificial light sensors.  Infection and negative reaction are the always-feared factors. It is imperative that all precautionary measures need to be ascertained.  One of the greatest challenges seems to be ensuring that the implant can remain in the eye for decades or more without causing scarring, immune system responses, and general degradation from daily biological wear and tear.  These artificial retinas are still years away from becoming widespread because they are too expensive, too clunky, and too fragile to withstand decades of normal wear and tear.Dept. of IT, GSSSIETW, Mysore 24
  25. 25. Bionic Eye: A Look into Current Research and Future ProspectsChapter 7 CONCLUSION This is a revolutionary piece of technology and really has the potential to changepeoples lives. Artificial Eye is such a revolution in medical science field. It’s good newsfor patients who suffer from retinal diseases. A bionic eye implant that could help restorethe sight of millions of blind people could be available to patients within two years. Retinal implants are able to partially restore the vision of people with particularforms of blindness caused by diseases such as macular degeneration or retinitispigmentosa. About 1.5 million people worldwide have retinitis pigmentosa, and one in 10people over the age of 55 have age related macular degeneration. The invention andimplementation of artificial eye could help those people. But whatever be the pro and cons of this system, if this system is fully developedit will change the lives of millions of people around the world. We may not restore thevision fully, but we can help them to least be able to find their way, recognize faces, readbooks, above all lead an independent life.Dept. of IT, GSSSIETW, Mysore 25
  26. 26. Bionic Eye: A Look into Current Research and Future ProspectsREFERENCES[1] ―Bionic Eye: What does the future hold‖ by Jack Kerouac.[2] ―A Bionic Eye comes to market‖ by Kurzweil Al.WEB REFERENCES[1][2][3][4][5] www.wikipedia.orgDept. of IT, GSSSIETW, Mysore 26