Abstract

SO.07.07

Chronic epiretinal implant in blind patients with retinitis pigmentosa: Long-term clinic results

Richard G.¹, Hornig R.², Keserü M.¹, Feucht M.^1
1Dept. of Ophthalmology, University Medical Center Hamburg-Eppendorf, Hamburg, ²IIP Technologies GmbH, Bonn

Objective: To evaluate the performance of a retinal implant system in blind patients with retinitis pigmentosa. Objectives of the study are also to test the feasibility of the surgical implantation method and the toleration of the implant by the eye over time, to control the wireless signal transmission for both data and energy and to evaluate the optimal stimulus parameters.
Methods: The study is an open, single center, pilot study. Four subjects with a visual acuity of light localisation or less recieved an implant. The retinal stimulator is fixed by a tack wich is inserted into the retina at a predifined location. The microcontact film is placed in the macular area and fixed with a silicon retainer ring. An extraocular part of the retinal stimulator is fixed onto the sclera. The implant carries 49 stimulation electrodes. The energy for the retinal stimulator is provided through a radio frequency transmission loop and the stimulation data is sent via an optical link.
Results: The implantation of the device proved to be surgically feasible. The follow-up period of more than 12 months clearly shows that the implants are very well tolerated in the patients eyes. There was no evidence of leakage, visible in the flouorescein angiogram and OCT. No incidence of cell growth has been observed. The fixation with one retina tack enables a close proximity between electrode array and retina. During the stimulation sessions the patients were able to distinguish between different points. When stimulating with multiple electrodes the subjects recognized simple patterns such as a horizontal bar. The threshold necessary for activation were lower than in the acute clinical trial.
Conclusions: Results from this trial demonstrate the feasability of a chronic retinal implant system to electrically stimulate the retina for eliciting perceptions resulting from defined input signals. The implant is well tolerated. The fixation is stable. No inflammatory reaction or cell proliferation was observed. The completely wireless data and energy transmission into the implant allow unrestricted eye movement and is therefore considered to be suitable as a long-term solution.

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