Visual Perceptions in an Acute Human Trial for Retina Implant Technology

Abstract

Abstract: : Purpose: To explore the visual perceptions evoked by acute electrical stimulation of the human retina in subjects suffering from retinitis pigmentosa with regard to the development of a chronic epi–retinal implant. Methods: A multicenter study with 20 subjects suffering from retinitis pigmentosa has been initiated. The study completely fulfills the conditions of the German medical device law, GCP–guidelines and the declaration of Helsinki. Ethical committees authorized the protocol. Subjects are examined extensively before inclusion to the study, after the operation and in the follow up. The electrical stimulation is done with a maximum duration of 45 minutes during a pars plana vitrectomy. After a local subconjuctival anesthesia four of the eye muscles are taken and fixated. A vitrectomy with focus on a complete removal of the vitreous is performed. For stimulation a microcontact film with IrOx–electrodes, manufactured by IIP–Technologies, Bonn, Germany, is used. Stimulation currents are in the limits of a chronic use. The film is positioned at the macula with a newly developed instrument, which is held by the surgeon for the duration of the operation. The microcontact film is connected by cable to a current generator, also manufactured by IIP–Technologies. After repeated stimulation, the microcontact film is removed and an extensive standardized interview is performed. Results: 6 of 20 subjects had been treated until abstract submission. All 6 subjects reported perceptions evoked by electrical stimulation. Even subjects with no light perception were able to see the electrical stimulation. Perception appeared when stimulation had been started and ended immediately after stimulation had been stopped. Most subjects reported yellow or blue objects. The brightness was described as clearly visible, comparable to the light of a candle. Perception size was generally small and reached from the size of a head of a match to the size of an apple as seen from a distance of one meter. All subjects reported that the perceptions were pleasant and not flashy. Conclusions: Electrical stimulation of the human retina using microcontact films creates useful visual perceptions even in totally blind patients. This may be a step towards the implantation of a chronic retina implant.

Keywords: retina • electrophysiology: clinical • clinical (human) or epidemiologic studies: systems/equipment/techniques