Abstract
Purpose::
To evaluate the performance of the first wireless 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. It is conducted under the terms and conditions of the Declaration of Helsinki and GCP-guidelines. Four subjects with a visual acuity of light localization or less received an implant. The Retinal Stimulator is fixed by a tack which is inserted into the retina at a predefined 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 and the stimulation data is sent via an optical link. The transmitter for both, energy and data, is embedded within a handheld unit.
Results::
The intraocular fixation (via tack) of the electrode array and the extraocular fixation of the device proved to be surgically feasible. The follow-up period of more than 9 months clearly shows that the implants are very well tolerated in the patient's eyes. No incidence of cell growth has been observed, no irritation has occurred as evidenced by fluorescein angiograms and optical coherence tomography. The fixation with one retina tack enables as close proximity between electrode array and retina. During the stimulation sessions the patients were able to distinguish between different points. Point to point discrimination was successful both horizontally and vertically. When stimulating with multiple electrodes the subjects have recognized simple patterns such as horizontal bar.
Conclusions::
Results from this trial demonstrate the feasibility of a chronic implant system to electrically stimulate the retina for eliciting perceptions resulting from defined input signals. The implant is well tolerated. The fixation is stable and no inflammatory reaction or cell proliferation has been observed. The completely wireless data and energy transmission into the implant allow unrestricted eye movement and is therefore considered suitable as a long-term solution.
Keywords: retinitis • low vision • retina