Ž . Brain Research 813 1998 181–186 Short communication Visual sensations produced by optic nerve stimulation using an implanted self-sizing spiral cuff electrode Claude Veraart a, ) , Christian Raftopoulos b , J. Thomas Mortimer c , Jean Delbeke a , Delphine Pins a , Geraldine Michaux a , Annick Vanlierde a , Simone Parrini a , Marie-Chantal Wanet-Defalque a ´ a Neural Rehabilitation Engineering Laboratory, UniÕersite Catholique de LouÕain, AÕenue Hippocrate, 54, UCL-54.46 B-1200 Brussels, Belgium ´ b Neurosurgery Department, St. Luc UniÕersity Hospital, B-1200 Brussels, Belgium c Applied Neural Control Laboratory, Department of Biomedical Engineering, Case Western ReserÕe UniÕersity, CleÕeland 44106-4912, USA Accepted 8 September 1998 Abstract A blind volunteer with retinitis pigmentosa was chronically implanted with a self-sizing spiral cuff electrode around an optic nerve. Electrical stimuli applied to the nerve produced localized visual sensations that were broadly distributed throughout the visual field and could be varied by changing the stimulating conditions. These results demonstrate the potential for constructing a visual prosthesis, based on electrical stimulation of the optic nerve, for blind subjects who have intact retinal ganglion cells. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Visual prosthesis; Retinitis pigmentosa; Optic nerve stimulation; Self-sizing spiral cuff electrode Following upon Brindley’s groundbreaking investiga- wx tion on occipital cortex stimulation 2 , several similar attempts to electrically evoke a visual sensation in blind w x individuals have been undertaken 6,13 . Recently, electri- cal stimulation of the peripheral visual system has also been suggested. In retinitis pigmentosa photoreceptor cells disappear, while ganglion cells and their axonal processes w x are spared 11,14 . Direct electrical activation of these cells w x using retinal implants is now investigated 7,12 . The work we report here consists in an alternative to retinal implant for vision rehabilitation in totally blind retinitis pigmentosa patients. Optic nerve electrical stimulation, with a multi- contact electrode and utilizing selective activation tech- w x niques 4,16 , provides an opportunity to create phosphenes over a wide portion of the visual field with only a few contacts and a few stimulators. Selected among six totally blind candidates with retini- wx tis pigmentosa 3 , a 59-year old female volunteer, who gave her informed consent, has been chronically implanted w x with a self sizing spiral cuff electrode 10,16 around her ) Corresponding author. Fax: q 32-2-764-9422; E-mail: veraart@gren.ucl.ac.be; URL: http:rrwww.md.ucl.ac.berentitesrfsior grenrintro.htm right optic nerve. This subject was affected by a dominant autosomal form of retinitis pigmentosa whose first symp- toms appeared when she was 28. She was left with a mere light perception from the age of 40, and was diagnosed totally blind at 57. This project fully complies with the Declaration of Helsinki, and was approved by the local Ethics committee. The four-contact self-sizing spiral cuff electrode was designed by the authors, in collaboration Ž . with NeuroTech Louvain-la-Neuve, Belgium , and fabri- Ž . cated by Axon Engineering Willoughby, OH 44094, USA . The electrode was intracranially implanted through a pteri- onal transsylvian approach and installed around the optic nerve after careful dissection of the arachnoidal strands. Electrode leads were brought outside the skull, and through Ž the skin where they ended in an external connector Fig. . 1. Stimulation started on day 2 post-surgery. Then the volunteer progressively worked up to a level of two 3-h- stimulation sessions a week. Charge balanced single pulses and trains were used. Stimulation was either monopolar, using a surface indifferent anode, or bipolar between two contacts within the cuff. Charge density was always kept Ž 2 . w below 150 mCr cm phase up to 50 Hz below 50 Ž 2 . x mCr cm phase up to 333 Hz , corresponding to a charge Ž . per phase of 300 nCrphase respectively 100 nCrphase 0006-8993r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S0006-8993 98 00977-9