This article is by Gail Johnson.
A device that uses no externally visible gear enables patients to read letters and see faces.
The German medical technology company Retina Implant developed the artificial retina, which was implanted in one eye of each participant as part of a company-funded trial. The patients had all been blinded by retinitis pigmentosa.
With the implant, eight of the nine patients in the trial could perceive light. Five were able to detect moving patterns on a screen as well as everyday objects such as cutlery, doorknobs, and telephones. Three were able to read letters. Seeing their own hands and the faces of their loved ones had the biggest impression on the patients.
The implanted device consists of a three-millimeter-square chip with 1,500 pixels. Each pixel contains a photodiode, which picks up incoming light, and an electrode and an amplification circuit, which boosts the weak electrical activity given off by the diode. A thin cable that runs through the eye socket connects the implant to a small coil implanted under the skin behind the ear, which means most of the system is invisible. The coil under the skin is powered by an external battery pack that can be held behind the ear with magnets.
The results follow an announcement earlier this week from California-based Second Sight that its Argus II system was approved for use in the United States (see “Bionic Eye Implant Approved for U.S. Patients”). The two technologies take different approaches to restoring vision in patients with retinal degeneration. In Second Sight’s system, a camera mounted on eyeglasses picks up images that are converted into electrical signals by a small wearable computer. That data is then sent to a 60-electrode chip to stimulate neurons in the retina. The Retina Implant device instead attempts to directly replace the lost photoreceptors, allowing the remaining retinal circuitry to do the data processing.
More than 20 groups worldwide are working on some form of visual prosthesis.
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