May 3, 2012
Eye Implants Help The Blind To See Again
|Two British men who have been totally blind for many years have had part of their vision restored after surgery to fit pioneering eye implants.|
This pioneering treatment is at an early stage of development, but it marks an important step forward in an effort to help those who have lost their sight from a condition known as retinitis pigmentosa.
Trials of the implant began in Germany six years ago and the first two British patients had the devices fitted in eight-hour operations last month.
The breakthrough was part of a clinical trial carried out at the Oxford Eye Hospital and King's College Hospital in London by Robert MacLaren and and Tim Jackson.
Jackson, an eye surgeon at King's College Hospital who fitted one of the devices, said:
"This pioneering treatment is at an early stage of development, but it is an important and exciting step forward, and may ultimately lead to a much improved quality of life for people who have lost their sight from retinitis pigmentosa.
"Most of the people who receive this treatment have lost their vision for many years, if not decades. The impact of them seeing again, even if it is not normal vision, can be profound, and at times quite moving."
Their work focuses on a previously untreatable condition known as retinitis pigmentosa (RP) - a type of inherited progressive retinal dystrophy in which abnormalities of the photoreceptors (rods and cones) or the retinal pigment epithelium (RPE) of the retina lead to progressive visual loss. The condition happens when the photoreceptor cells at the back of the eye gradually cease to function.
While the procedure did not restore complete vision to the patients, it did restore their ability to perceive light and even some shapes. This is no small thing for the visually impaired, as even the slightest hints of light and shape can help an individual navigate through their environment.
To make this happen, MacLaren and Jackson developed a microchip that could be fitted behind the retina. The wafer-thin, 3mm square chip has 1,500 light-sensitive pixels which take over the function of the failed photoreceptor rods and cones. In this sense, it can be seen as a kind of transplant, in which original function has been replaced by an artificial device. Once implanted behind the retina, a fine cable runs to a control unit under the skin behind the ear.
The pixels on the chip are stimulated when light enter the eye. In turn, it sends a signal to the optic nerve and from there to the brain. The end result is the perception of light. The patient can alter sensitivity by using a power unit which connects to the chip via a magnetic disc on the scalp.
When the surgery was complete, the patients were able to stand in a room and perceive light coming through windows. They were also capable of making out a curve or a straight line when close-up. And in an unexpected benefit, one patient claims that the implant has given him the ability to dream in color for the first time in 25 years.
MacLaren and Jackson stress that the chip is not a treatment but part of a clinical trial. The next phase will see up to a dozen British patients fitted with the implants.
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