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Nigeria Today Online
 Apr 28, 08 - 1:15 PM |
Artificial eye implant raises hope for blindness cure
Artificial eye implant raises hope for blindness cure SCIENTISTS have reported huge success in the first clinical trials of an artificial eye implant, bionic eye. A team at London's Moorfields Eye Hospital, United Kingdom, have carried out the treatment on the first patients as part of a clinical study into the therapy. The artificial eye, connected to a camera on a pair of glasses, has been developed by United States firm Second Sight. It said the technique may be able to restore a basic level of vision, but experts warned it was still early days. The trial aims to help people, who have been made blind through retinitis pigmentosa, a group of inherited eye diseases that affects the retina. The disease progresses over a number of years, normally after people have been diagnosed when they are children. It is not known whether the treatment has helped the two patients - both men in their fifties - to see and any success is only likely to be in the form of light and dark outlines, but doctors are optimistic. Earlier in the month, U.S. and German scientists announced that they have designed a bionic eye to allow blind people to see again. It comprises a computer chip that sits in the back of the individual's eye, linked up to a mini video camera built into glasses that they wear. Images captured by the camera are beamed to the chip, which translates them into impulses that the brain can interpret. The work was discussed at a British Royal National Institute of the Blind talk. Indeed, the Boston Retinal Implant Project recently developed a bionic eye implant that will restore vision to those affected by degenerative blindness. The device works by being implanted into the back of the eyeball and working as a light transmitter to the brain, where the two are connected by a nerve/wire thinner than a human hair. But the technology has its limitations, it would not give sight to those born blind or who suffer glaucoma, nor will it offer perfect vision. Only for those, who previously had sight, and a semi-functional optical nerve, is this possible. The idea is that it will give the blind a general sense of their surroundings so they can function on a basic level. But researchers do hope to improve the technology so that users can recognise things like facial detail and expressions in the future. Prof. Gislin Dagnelie, of Johns Hopkins University, Baltimore, unveiled details at the conference in London, the UK. Human trials will begin within a year, Dagnelie said. Although the images produced by the artificial eye were far from perfect, they could be clear enough to allow someone, who is otherwise blind to recognise faces, he said. The breakthrough is likely to benefit patients with the most common cause of blindness, macular degeneration. This occurs when there is damage to the macula, which is in the central part of the retina where light is focussed and changed into nerve signals in the middle of the brain. The implant bypasses the diseased cells in the retina and stimulates the remaining viable cells. Lyndon da Cruz, the eye surgeon, who carried out the operations last week, said the treatment was "exciting." "The devices were implanted successfully in both patients and they are recovering well from the operations." Other patients across Europe and the U.S. have also been involved in the trial. The bionic eye, known as Argus II, works via the camera which transmits a wireless signal to an ultra-thin electronic receiver and electrode panel that are implanted in the eye and attached to the retina. The electrodes stimulate the remaining retinal nerves allowing a signal to be passed along the optic nerve to the brain. Earlier this year, three people were successfully implanted with a permanent "retinal prosthesis" by researchers at the Keck School of Medicine of the University of Southern California. Each patient wore spectacles with miniature video cameras that transmitted signals to a 4-mm-by-5-mm retinal implant via a wireless receiver embedded behind the ear. The device works by transmitting visual signals captured by the video camera to the retinal implant, which contains an array of 16 electrodes. The signal is then recreated by stimulating the remaining healthy retinal cells with the electrodes, which pass on the information to the brain through the optic nerve. Dr. Mark Humayun, professor of ophthalmology at the Keck School, said the first target population would be those who had had sight once and then lost it due to certain types of blindness such as retinitis pigmentosa or age-related macular degeneration. "If successful in these patients, then the device will be evaluated for use in other types of blindnesses, such as those blind from birth," Humayun said. Test results so far have revealed that some patients were capable of detecting when a light was turned on or off, describing the motion of an object and counting discrete objects. The capability to recognise faces or read large print is thought to be possible only with 1,000 or more electrodes, however. Australian researcher Nigel Lovell, from the University of New South Wales, is working on an implant with 100 electrodes, which he hopes will give patients the ability to differentiate between night and day, detect obstacles and provide some rudimentary reading skills. "100 channels is near the practical limit," said Lovell. "There are ways around these limits, but it's not the most important question at present." While these approaches focus on the camera being outside the body, Dr. Alan Chow of Optobionics hopes to develop a silicon retina that has the sensing equipment onboard - 4,000 to 5,000 microscopic solar cells that function in place of the eye's natural sensors. Putting in the all the electronics, though, may prove to be a problem, since the eye is a corrosive environment where electronics don't do too well. "Certain materials have been shown to be biocompatible and thus will exist in the body without major tissue reactions," said Lovell in an e-mail. "Chow's devices have not been shown (at least to my knowledge) to be biocompatible." A pea-size Implantable Miniature Telescope, or IMT, embedded in only one eye is the basis of the work done by California-based VisionCare Ophthalmic Technologies. Replacing the eye's lens, the telescope projects images over the undamaged area of the retina and provides central, "straight-ahead" vision while the other eye handles peripheral vision. The technology aids those, who haven't totally lost sight from blinding diseases. For those whose peripheral vision remains intact, the IMT could prove to be a great blessing. "Central vision is the most important for functional and detailed everyday tasks," said Chet Kumar, VisionCare's director of business and market development. "You need your central vision to read a recipe, recognise people and to view the computer or TV screen." So far, the majority of patients implanted with the device have generally improved two to three lines of vision on the eye chart. Currently in the last phase of clinical trials, the company is enrolling 200 patients for a two-year study, by the end of which they hope to have enough data to earn Food and Drug Administration market approval. "Our goal is to help these individuals regain some degree of functional vision," said Kumar. "Though not a cure, we hope that they will be able to go about their daily activities and hobbies more independently." Bypassing the need to have intact retinas entirely, the Dobelle Institute's brain implant approach uses an external camera and directly interfaces with the brain through electrodes attached to the visual cortex. While this technique offers treatment for a wider variety of vision problems, considerable difficulties exist in mapping the stimulation sites in the brain. Though the bionic eye is still at least five years away by most estimates, experts are nevertheless hopeful. "While good progress is being made on both the retinal and the cortical (brain) chip implants, it is not clear if either of these approaches will finally work," said Dr. Gerald Chader, the chief scientific officer of the Foundation Fighting Blindness. "While much of the work is still preliminary, we are very hopeful that one day these implants could restore ambulatory vision to patients," he added. David Head, chief executive of the British Retinitis Pigmentosa Society, said: "This treatment is very exciting, but it is still early days. "There is currently no treatment for patients so this device and research into stem cells therapies offers the best hope." Prof. Dagnelie said: "The retinal implant contains tiny electrodes. If you stimulate a single electrode, the person will see a single dot of light." They have already tested implants containing a handful of electrodes, but the end device will contain 50-100 to give a better overall picture. "We are hoping this will be enough for the person to be able to make their way through a building, find a door or window and avoid obstacles for example. "To us, the images look very basic but for someone, who was previously blind they are a massive step forward." But he added, "there is still quite a bit of work that will be needed to fine tune it. Being able to see faces will be quite a bit down the line." He said training the individual to learn how to interpret the blurry images should help. Anita Lifestone of the RNIB, said, "this is a revolutionary piece of technology and really has the potential to change people's lives. But we need to be aware it is still some way in the future." Courtesy - Nogeria Today Online |
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