Implant may restore sight to the blind

A clinical trial of an electronic subretinal prosthesis has successfully allowed blind patients to recover some perception of single and multiple phosphenes, as well as horizontal and vertical lines, reported Eberhart Zrenner, MD, at the joint meeting of the European Society of Ophthalmology and American Academy of Ophthalmology.

The device, developed in Germany, consists of a chip with 16 DS electrodes and a subdermally implanted power line, which connects the chip to an external energy supply. One end of the power line is clamped behind the ear and the skin is tunnelled from this point to the upper fornix of the eye. A small scleral flap is created to uncover the choroids and, with the help of a guiding foil, the implant is slid under the retina. A small piece of the retina is preventively detached with a small bleb of fluid, which is eventually removed and replaced with silicone oil.

The prosthesis was implanted for 30 days in seven patients who had had no useful vision for at least five years. All operations were performed without complication. All but one patient was able, in various degrees, to recover perception of single and multiple phosphenes, horizontal and vertical lines and even direction of localized bright objects in dim light. One patient, with the consent of the researchers, has kept the prosthesis in and this may help provide useful, long-term information on biocompatibility.

Further, longer-term studies with an updated version of the implant are currently being planned.