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Useful vision restored in retinitis pigmentosa patients who received subretinal implant
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More than half of patients with severe retinitis pigmentosa who received the Alpha IMS subretinal implant recovered functional vision, according to results from a second human clinical trial of the device.
The trial examined nine patients for a 3- to 9-month period after subretinal implantation of the Alpha IMS (Retina Implant), a 3 mm × 3 mm, 1,500-pixel device designed to restore vision without externally visible equipment.
Each pixel has a photodiode, an amplification circuit and an electrode to allow an electrical impulse to be delivered to retinal layers corresponding to incoming light.
The chip, placed beneath the foveal region, works via inductive energy transfer from a battery pack in the control unit that allows the user to adjust brightness and contrast of perception. It offers a 10° × 10° diamond-shaped visual field that is roughly 15° diagonal.
One subject was excluded from follow-up due to intraoperative complications, but five of the remaining eight subjects reported functional vision improvements, including near vision recognition of facial characteristics and clothing patterns and ability to distinguish objects such as telephones, cutlery, door knobs and signs on doors. Far-vision improvements included ability to see the horizon and objects on the horizon.
A multicenter phase of the trial already has begun.
Another retinal implant for patients with advanced retinitis pigmentosa, the Argus II Retinal Prosthesis System (Second Sight Medical Products), was recently approved by the U.S. Food and Drug Administration.
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