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How does a "bionic eye" allow blind people to see?

In the past 20 years, biotechnology has become the fastest-growing area of scientificresearch, with new devices going into clinical trials at a breakneck pace. bionic armallowsamp!tees to control movements of the prosthesis with their tho!ghts. training system calledrain#ortis letting people with vis!al and balance disorders bypass their damaged sensoryorgans and instead send information to theirbrainthro!gh the tong!e. $ow, a company called%econd %ight has received &' approval to begin (.%. trials of a retinal implant system thatgives blind people a limited degree of vision.

)he rg!s II *etinal #rosthesis %ystem can provide sight -- the detection of light-- topeople who have gone blind from degenerative eye diseases like mac!lar degeneration andretinitis pigmentosa. )en percent of people over the age of ++ s!ffer from vario!s stages ofmac!lar degeneration. *etinitis pigmentosa is an inherited disease that affects abo!t .+million people aro!nd the globe. oth diseases damage the eyes photoreceptors, the cellsat

the back of the retina that perceive light patterns and pass them on to the brain in the form ofnerve imp!lses, where the imp!lse patterns are then interpreted as images. )he rg!s IIsystem takes the place of these photoreceptors.

)he second incarnation of %econd %ights retinal prosthesis consists of five main parts

digital camerathats b!ilt into a pair of glasses. It capt!res images in real time and

sends images to a microchip. video-processing microchip thats b!ilt into a handheld !nit. It processes images

into electricalp!lses representing patterns of light and dark and sends the p!lses to aradio transmitter in the glasses.

radiotransmitter that wirelessly transmits p!lses to a receiver implanted above the

ear or !nder the eye

radio receiver that sends p!lses to the retinal implant by a hair-thin implanted wire

retinal implant with an array of /0 electrodes on a chip meas!ring mm by mm

)he entire system r!ns on abatterypack thats ho!sed with the video processing !nit.hen the camera capt!res an image -- of, say, a tree -- the image is in the form of light anddark pi1els. It sends this image to the video processor, which converts the tree-shaped pattern

of pi1els into a series of electricalp!lses that represent "light" and "dark." )he processorsends these p!lses to a radio transmitter on the glasses, which then transmits the p!lses inradio form to a receiver implanted !nderneath the s!bects skin. )he receiver is directlyconnected via a wire to the electrode array implanted at the back of the eye, and it sends the

p!lses down the wire.

hen the p!lses reach the retinal implant, they e1cite the electrode array. )he arrayacts as the artificial e3!ivalent of the retinas photoreceptors. )he electrodes are stim!lated inaccordance with the encoded pattern of light and dark that represents the tree, as the retinas

photoreceptors wo!ld be if they were working 4e1cept that the pattern wo!ldnt be digitallyencoded5. )he electrical signals generated by the stim!lated electrodes then travel as ne!ral

signals to the vis!al center of thebrainby way of the normal pathways !sed by healthy eyes --the optic nerves. In mac!lar degeneration and retinitis pigmentosa, the optical ne!ral

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pathways arent damaged. )he brain, in t!rn, interprets these signals as a tree and tells thes!bect, "6o!re seeing a tree."

It takes some training for s!bects to act!ally see a tree. t first, they see mostly lightand dark spots. !t after a while, they learn to interpret what the brain is showing them, and

they event!ally perceive that pattern of light and dark as a tree.

)he first version of the system had / electrodes on the implant and is still in clinicaltrials at the (niversity of 7alifornia in 8os ngeles. 'octors implanted the retinal chip in si1s!bects, all of whom regained some degree of sight. )hey are now able to perceive shapes4s!ch as the shaded o!tline of a tree5 and detect movement to varying degrees. )he newestversion of the system sho!ld offer greater image resol!tion beca!se it has far more electrodes.If the !pcoming clinical trials, in which doctors will implant the second-generation deviceinto 9+ s!bects, are s!ccessf!l, the retinal prosthesis co!ld be commercially available by200. )he estimated cost is :;0,000.

*esearchers are already planning a third version that has a tho!sand electrodes on theretinal implant, which they believe co!ld allow for facial-recognition capabilities.

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