Purpose: Electrical stimulation of retinal neurons has been shown to be a feasible way to elicit visual percepts in patients blind from retinal degenerations. The EPIRET3 retinal implant is the first completely wireless intraocular implant for epiretinal stimulation. Stimulation tests have been performed during a clinical trial that was carried out at the eye clinics of Aachen and Essen to evaluate the safety and the efficacy of the implant.
Methods: Six legally blind retinitis pigmentosa patients were included in the study. In accordance with the regulations laid down in the study protocol, three 1-hour perceptual tests for each subject were performed within 4 weeks of surgery. Stimuli were charge-balanced square current pulses of various durations and current amplitudes.
Results: All subjects reported visual percepts as a result of electrical stimulation by the implant. Thresholds for eliciting visual percepts varied between them but were below the safety limits of electrical stimulation. Stimulation success depended stronger on pulse duration than on current amplitude or total charge delivered. Subjects were able to discriminate between stimulation patterns of different orientations or at different locations of the electrode array.
Conclusions: The EPIRET3 system is suitable to elicit visual percepts in blind retinitis pigmentosa patients.