Wireless Epiretinal Prosthesis for Patients with Retinal Degenerative Disease

Encouraging early outcomes in subjects with no or minimal light perception.

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Encouraging early outcomes in subjects with no or minimal light perception. Cheryl Guttman Krader reports. A wireless epiretinal visual prosthetic device (NR600, Nano Retina) appears promising in early clinical trials, providing improvements in visual capabilities—as demonstrated by daily life task performance in patients with end-stage retinitis pigmentosa. Peter Stalmans MD, PhD is an investigator in the first in-human study of the prosthetic system and has performed five of the eight implantations completed so far. He presented follow-up data from five patients seen between 30 days and 20 months post-surgery. “All eyes tolerated the implantation procedure and had a good postoperative recovery. There have been no cases of device migration, the fundus remains clear with no signs of fibrosis around the implant, and OCT imaging shows only slight tissue elevations immediately adjacent to the implant in some cases. However, there is no thinning or morphological changes of the retina in the vicinity of the device,” Professor Stalmans reported. NOVEL DESIGN The epiretinal prosthesis is an all-in-one system comprised of an onboard camera powered by infrared panels, an image processing unit, and 600 isolated electrodes that penetrate the retina. It has no cables exiting the eye. Instead, dedicated rechargeable eyeglasses worn by the patient provide power to the device and modulate the stimulus via an infrared signal. Describing other unique features of the system, Prof Stalmans noted the electrodes penetrating the retina allow focal activation and at thresholds two orders of magnitude lower than what is required for the Argus II retinal prosthesis. Also, in distinction to competing epiretinal prostheses attached to the retina with a tack, the NR600 implant is fixed using an alternative method that does not involve application of direct force onto the retina. Instead, helical springs extending from a ring sutured into the anterior sulcus keep the implant in place. Prof Stalmans illustrated the fixation method and implantation of the prosthesis through a surgical video. He also demonstrated the clinical benefit of the prosthetic system through a video showing a patient walking, eating, locating his refrigerator, and retrieving an item from inside the refrigerator while wearing the NR600 eyeglasses. “Of course, patients need to follow a very intensive rehabilitation programme. In addition, functioning with the system is mentally challenging and fatiguing, so patients do not use it all day. However, this particular patient told me he had an unannounced visit from friends and was so happy that by using the prosthesis, he was able to open the door and welcome them inside,” Prof Stalmans said. STUDY OUTCOMES The clinical trial is evaluating safety as its primary outcome. So far, adverse events considered related to the surgery or the device consist of mild postoperative corneal oedema, elevated IOP, and mild scleritis. “All of the events were transient and responded to medication,” Prof Stalmans said. When asked about their visual capabilities using the prosthesis, two of the five patients with follow-up data reported being highly satisfied with their improvements, one was satisfied, and the remaining two patients were neutral. The study was presented at the 2021 American Academy of Ophthalmology Retina Subspecialty Day in New Orleans, Louisiana, USA. Prof Peter Stalmans MD, PhD, is a member of the Department of Ophthalmology and Vitreoretinal Surgeon at UZ Leuven, Belgium, and Associate Professor of Ophthalmology at KU Leuven, Belgium. peter.stalmans@uzleuven.be