May 26, 2003.
There's light at the end of the tunnel for people who are blinded by degenerative eye disease.
The recent development of a bionic retina, which may even help blind children to see one day, shows promise.
According to the researchers, the device has already been tested in three patients. The "bionic retina" consists of a thin sliver of platinum and silicone, studded with electrodes. It is about a third of the size of a contact lens and is placed on top of the retina.
How it works.
The device works by stimulating the remaining retinal cells, which pass visual information on to the brain via the optic nerve, with electronic impulses. It enables patients to detect light and distinguish between objects, Dr Mark Humayun, professor of ophthalmology at the University of Southern California, USA, said.
He announced the group's findings at a meeting of the Association for Research in Vision and Ophthalmology in Florida last week.
The instrument is designed to replace the damaged retinal cells in the eyes of people suffering from blinding diseases, like macular degeneration and retinitis pigmentosa.
Macular degeneration is a progressive eye condition in which the part of the retina called the macula is damaged, resulting in lost central vision. This disease is the leading cause of blindness in elderly people.
Three patients already received device The first implant of the device took place in February 2002, the second in July 2002 and the third in March this year.
According to Humayun, the bionic implant doesn't process light directly. The trial patients all received pairs of glasses mounted with minute video cameras. The purpose of these cameras was to transmit images to a wireless receiver, which relayed the signals to the bionic devices in the individual patients' eyes. In the eyes, the original images were recreated by lighting up the appropriate electrodes.
"There are a lot of advantages to using it," Humayun said, pointing out that the camera has zoom features and that colours can be adjusted.
Vision isn't as sharp with device But the device has its downside. Since it has only 16 electrodes, vision isn't as sharp as is the case in people with normal vision. Later versions of the device might contain as much as 1 000 electrodes. These will make vision clearer.
"The eye has millions of light-sensing cells. Our results are a testament to the brain's ability to use crude information and make sense of it," he said.
Humayun believes that this device might eventually be used in a similar way as cochlear implants are used in deaf children.
This would, of course, mean that the bionic retina would also have to be implanted in early childhood to have the desired effect.
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