May 9, 2003.
A "bionic" eye that can help the blind to see has restored partial vision to three people who lost their sight because of incurable disease.
The results of the first clinical trial of an artificial retina implanted into the eye showed that it worked well enough to allow the blind to distinguish light from dark and even to see simple objects.
Each patient had an operation to have the implant fitted over their own damaged retinas. They wore spectacles fitted with miniature video cameras, which transmitted signals to the implanted device.
All the patients could see far better with the device switched on and one of them could even tell the difference between everyday objects.
Scientists from the University of Southern California in Los Angeles released details of the clinical trial yesterday to the annual meeting of the Association for Research in Vision and Ophthalmology in Fort Lauderdale, Florida.
Mark Humayun, professor of ophthalmology at the university's Keck School of Medicine, said the trial broke new ground, showing that an electrical implant in the eye could restore at least the partial sight of people suffering from diseases such as retinitis pigmentosa and macular degeneration. "We have found that the devices are indeed electrically conducting, and can be used by the patients to detect light or even to distinguish between objects such as a cup or plate in forced-choice tests conducted with one patient so far," Professor Humayun said.
The trial, which was approved by the US Food and Drug Administration, was only designed to demonstrate the essential safety of an electronic retina implant and further, long-term trials are planned to assess its usefulness.
The implant had 16 electrodes, which electrically stimulated the remaining healthy cells of the patient's retina in a pattern that depended on the nature of the signals received from the video cameras.
The patient's own optic nerve transmitted the signals to the visual centres of the brain where they were used to distinguish light from dark, movement and rudimentary shapes.
All tests were based on viewing a computer screen with images of letters or objects. "We plan in the near future to look at how useful the prosthesis can be in activities of daily living," Professor Humayun said.
Each implant measures 4mm by 5mm and is connected via a small cable to a wireless receiver implanted under the skin above the ear, which picks up signals transmitted from miniature video cameras worn on the spectacles.
Professor Humayun said that the initial aim was to allow blind people to perform simple tasks around the house. "Pouring water into a cup, sitting at a table being able to see your plate, your fork and knife. And then beyond that, can they recognise maybe the facial features of their loved ones? Those are things we would like to get to," he said.
The first patient received the implant in February 2002, the second had the operation in July and the third in March this year. None of them has reported finding the prosthesis uncomfortable.
Although components of the devices have been tested in the past, the tests were only temporary, with the prosthesis removed after less than an hour.
The latest trial, though, was intended to be a permanent implant with the electronics being left in place indefinitely unless complications occurred and they had to be removed, Professor Humayun said.
In the future, light-sensitive electrodes might be able to be used. They could directly detect any light entering the eye rather than having to rely on video signals from cameras.
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