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P. Walter, W. Mokwa, A. Messner, EPIRET3; The EPIRET3 Wireless Intraocular Retina Implant System: Design of the EPIRET3 Prospective Clinical Trial and Overview. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3023.
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To demonstrate the feasibility, efficacy and safety of a completely implantable intraocular retinal prosthesis to restore vision in blind RP subjects.
The EPIRET3 device - a wireless remotely controlled and fully intraocular 25 electrode system for epiretinal electrical stimulation - was implanted in six blind subjects enrolled in a prospective exploratory clinical trial. After four weeks the implant was removed. Visual sensations were elicited in three stimulation sessions in week 1, 2, and 4. Standard clinical examinations, electrophysiology, fluorescein angiography and quality of life exams were performed. For implantation the lens or artificial lens was removed, a ppV was performed and the implant was inserted with the receiver part in the sulcus ciliaris and the stimulator part placed on the posterior pole and fixated here with two retinal tacks. Stimulation was performed with biphasic pulse sequences at single electrodes and at simple electrode patterns. Activation of the implant was confirmed by recording of stimulus artefacts with conjunctival electrodes. The patient was asked to press buttons when visual sensations were induced. Primary endpoint of the study was the observation of visual sensations induced with the device. Secondary endpoints were visual acuity, adverse events, clinical findings and QoL.
In all six patients the EPIRET3 device could be implanted and explanted successfully. In all six patients visual sensation could be elicited. The mean stimulus intensity at threshold for visual sensations varied between 2.2 and 73.2 µC/cm2. Adverse events were observed as a severe inflammatory non-bacterial response in one case after implantation and a retinal hole requiring silicone oil filling in one case during explantation.
The EPIRET3 concept was suitable to elicit visual sensations in blind RP subjects. The implant was well tolerated, the surgery is feasible, the stimulation thresholds were considerably below the limit for toxic currents in chronic neural tissue stimulation. The EPIRET3 system proves that it is possible to fabricate a fully implantable wireless retinal implant without any cable crossing the wall of the eye which could be an advantage in long-term biocompatibility.
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