- Device replaces the function of rods and cones in the back of the eye
By Claire Bates
PUBLISHED: 11:04 EST, 14 June 2012 | UPDATED: 11:06 EST, 14 June 2012
A retinal implant could one day be used to restore vision lost through injury or disease, after it gave a brief glimpse of light to a group of patients.
The device is the creation of Shawn Kelly from Carnegie Mellon University in Pittsburgh, and the result of a decade’s worth of research.
It is made up of two tiny cameras attached to a pair of glasses which send images to a computer chip attached to the patient’s eye. The chip turns the images into an electrical current sent along a wire to a film inserted behind the retina.
Mr Kelly said: ‘From this thin plastic film, the width of an eyelash, flexible electrodes send stimulating current signals to retinal nerves, helping to restore vision.
‘My device very much like a camera, replacing the function of the rods and cones in the human eye.’
In basic terms the eye operates on the same principle as a camera. The eye, however, takes two simultaneous pictures, one in black and white, the other in colour.
Cells in the retina, called rods, register black and white only; they are so sensitive they can detect light as faint as 100-trillionth of a watt. Other retinal cells, the cones, are affected by color and are most abundant at the fovea, the place where the image falls when the eye focuses.
The blind spot, lacking both rods and cones, is where the optic nerve leaves the retina, carrying the pictures for the brain to see.
So far the device has been successfully tested on a small group of blind patients, who reported seeing patches of light and dark and some shapes.
Mr Kelly said: ‘My tools are designed to help individuals struggling with blindness, and to ultimately help injured veterans with head and eye wounds recover some peripheral vision.’
The device can only create an image with a resolution of 256pixels because that’s how many electrodes can currently fit onto the back of the film.
However, Mr Kelly said the device was extremely stable and wouldn’t deteriorate because no water vapour can get into the well-sealed processor.
This month the pioneering scientist was awarded a four-year grant of $1.1million from the U.S Department of Veterans Affairs to continue work on the retinal prosthesis.
‘This is wonderful support for work so critical to millions of Americans battling vision issues,’ Mr Kelly said.
A similar device is being trialed by patients in the UK although this powered by light entering the eye directly rather than images sent from cameras.
Chris James and Robin Millar lost their vision because of a condition known as retinitis pigmentosa, where the photoreceptor cells at the back of the eye gradually cease to work.
They underwent a 10-hour operation to insert the wafer-thin microchip in the back of one eye at the Oxford University Eye Hospital.
Mr James said once his brain adjusted he was able to detect the curves and outline of objects.
Ten more Britons with RP will be fitted with the implants, which are also being tested in Germany and China. The device, made by Retina Implant AG of Germany, connects to a wireless power supply buried behind the ear.
This is connected to an external battery unit via a magnetic disc on the scalp. The user can alter the sensitivity of the device using switches on the unit.