Epiretinal Prosthesis Implantation in Humans

Abstract

Abstract: : Purpose: To describe and evaluate implantation of the Second Sight (SS)–Model 1 intraocular retinal prosthesis (IRP) in 6 subjects with bare or no light perception from end–stage retinitis pigmentosa. Methods: The FDA granted an IDE, the USC–IRB approved the study protocol, and informed consent was obtained. The IRP was implanted in the worse eye of 6 subjects (2 men and 4 women) who met the study criteria. The IRP includes an extraocular microelectronic device, an intraocular electrode array with a 4x4 grid of platinum electrodes embedded in silicone rubber connected by a multiwire cable, and a mini video camera. The stimulator was surgically placed in the temporal bone and the electrode cable was placed under the temporal skin connecting to the orbit. A pars plana vitrectomy was performed and the electrode array was secured over the macula with a retinal tack. During follow–up visits, subjects underwent routine anterior and posterior segment examination, fluorescein angiography, color photography and optical coherence tomography (OCT). Electrical stimulation with threshold measurement and camera testing were performed on all subjects. Results: All subjects had successful surgical implantation of the SS model–1 IRP. As of November 2004 subjects 1 (S1), 2 (S2), 3 (S3), 4 (S4), 5 (S5), 6 (S6) have been implanted for 33, 28, 19, 7, 6, and 5 months respectively. The intraocular stimulating array remained in position to activate the retina and produce phosphenes in all 6 subjects as noted during eye examination, color photography, fluorescein angiography and OCT. The tack did not dislodge from the retina, except in one patient who had a blunt eye trauma resulting in the electrode array and tack separating the retina. The array was repositioned with a second surgery. No subject developed vitreous hemorrhage, subretinal bleeding, or intraocular infection during follow–up. Using a head–mounted video camera as a stimulus source, all 6 subjects detected room lights on/off and light location with high accuracy. Other results for the first 3 subjects included finding objects (3AFC) 84% (p< .001); counting objects (4AFC) 74% (p< .001); recognizing objects (3AFC) 63% (p< .001); L position (4AFC) 61% (p< .001). Conclusions: The SS–Model 1 IRP was chronically implanted in humans for over 2.5 years and preliminary functional testing of artificial vision showed a significantly improved ability to perform selected tasks. Further developments in design and surgical technique are in progress.

Keywords: retina • retinal degenerations: hereditary • vitreoretinal surgery