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Bionic eyes offer hope for the blind23 February 2007 Last week, researchers from the University of South Carolina Doheny Eye Institute announced their plans to develop an implant that could one day restore sight to millions. Speaking at the American Association for the Advancement of Science (AAAS) annual meeting in San Francisco, lead researcher Professor Mark Humayun revealed that the Food and Drug Administration (FDA) has approved a second clinical study of their novel device, the Argus II Retinal Prosthesis System. What is the Argus II?The Argus II, which is being developed in a joint venture with Second Sight Medical products, is an electronic retinal implant designed to treat blindness caused by retinitis pigmentosa (RP). RP is an inherited condition that causes cells in the retina - which detect light - to degenerate. It leads to a gradual loss of vision and eventual blindness. An early version of the Argus has already shown promise. "The first phase of our implant work began in 2002," said Humayun. "We have successfully implanted six patients in the trial and we have found that the devices are indeed electrically conducting and can be used by patients to detect light or even to distinguish between objects such as a cup or plate." How does the Argus II work?The Argus II implant works in conjunction with an external camera. An implant is attached to the retina during surgery. Images from the external camera, which can be mounted on glasses, are sent to the implant. The implant generates electrical impulses which are relayed to the brain - where they are interpreted as a rudimentary form of vision. The first generation Argus had 16 electrodes laid out in an array. The Argus II has 60, and it's hoped that this will lead to a better resolution of image. It is also about a quarter of the size of the original, so it should be quicker and easier to implant. The device may also one day be able to cure age-related macular degeneration (AMD), a condition which also causes cells in the retina to degenerate. Together with RP, they account for around 25 million cases of blindness or severe vision loss worldwide, explained Humayun. What is AMD?AMD is the most common cause of blindness in the UK and, as the name suggests, it increases with age. It is associated with a number of risk factors, including smoking, a poor diet and ultraviolet light. There are two types of AMD.
How is AMD currently treated?At the moment there is no specific treatment for dry AMD. Little is known about the underlying causes of the disease, although research is ongoing. Advice for slowing it's progression includes giving up smoking and eating a healthy diet with plenty of green vegetables. There are a number of drugs currently being used and under development for wet AMD. These work by stopping abnormal blood vessel growing, and have shown some promising results. There are also types of laser surgery available which can help slow the progression of wet AMD in some patients. They work by sealing and stopping the growth of blood vessels over the retina. Looking aheadIt's hoped that the Argus device may eventually provide another treatment option for people affected by RP and AMD. For their next trial, the team will recruit volunteers aged over 50 who have lost their sight to these conditions. "We will be able to test the new device with patients at their homes, churches, schools and similar locations," Professor Humayun added. "The importance of this work is going to be reflected in how well this helps them regain some of their lost vision." Further information
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