Electronic subretinal prosthesis recovers visual perception in blind patients

VIENNA — The first clinical trial of an electronic subretinal prosthesis developed in Germany found that the device allowed blind patients to recover perception of single and multiple phosphenes and horizontal and vertical lines. Patients also could recognize the direction of movement and localized bright objects in dim light.

The device consists of a chip with 16 DS electrodes and a power line implanted subdermally, connecting the chip to an external energy supply. The prosthesis was implanted for a testing period of 30 days in seven patients with no useful vision for at least 5 years. Efficacy and safety of the implant were evaluated.

"Implantation starts from behind the ear, where one end of the power line is clamped. The skin is tunneled from this point to the upper fornix of the eye. A small scleral flap is then performed to uncover the choroid, and with the help of a guiding foil, the implant is slid under the retina. A small portion of the retina is preventively detached with a small bleb of fluid, which is eventually removed an replaced with silicone oil," said Eberhart Zrenner, MD, at the joint meeting of the European Society of Ophthalmology and American Academy of Ophthalmology.

All operations were performed successfully without complications and results were rewarding.

"We have not yet achieved a perfect outcome. We had one failure and a lot of individual variation in the quantity and quality of perception. However, patients were happy and described this as an important positive experience. All of them said they would be ready to do it again, and one patient decided, with our consent, to keep the prosthesis. This will give us useful information on the long-term biocompatibility of the device," Dr. Zrenner said.

More long-term studies will soon be performed with an updated prototype of the prosthesis, implanted for 3 to 6 months.