Abstract
Objective. The restoration of vision in blind patients suffering from degenerative retinal diseases like retinitis pigmentosa may be obtained by local electrical stimulation with retinal implants. In this study, a very large electrode array for retinal stimulation (VLARS) was introduced and tested regarding its safety in implantation and biocompatibility. Further, the array’s stimulation capabilities were tested in an acute setting. Approach. The polyimide-based implants have a diameter of 12 mm, cover approximately 110 mm2 of the retinal surface and carrying 250 iridium oxide coated gold electrodes. The implantation surgery was established in cadaveric porcine eyes. To analyze biocompatibility, ten rabbits were implanted with the VLARS device, and observed for 12 weeks using slit lamp examination, fundus photography, optical coherence tomography (OCT) as well as ultrasound imaging. After enucleation, histological examinations were performed. In acute stimulation experiments, electrodes recorded cortical field potentials upon retinal stimulation in the visual cortex in rabbits. Main results. Implantation studies in rabbits showed that the implantation surgery is safe but difficult. Retinal detachment induced by retinal tears was observed in five animals in varying severity. In five cases, corneal edema reduced the quality of the follow-up examinations. Findings in OCT-imaging and funduscopy suggested that peripheral fixation was insufficient in various animals. Results of the acute stimulation demonstrated the array’s ability to elicit cortical responses. Significance. Overall, it was possible to implant very large epiretinal arrays. On retinal stimulation with the VLARS responses in the visual cortex were recorded. The VLARS device offers the opportunity to restore a much larger field of visual perception when compared to current available retinal implants.
Highlights
Retinitis pigmentosa (RP) is a retinal dystrophy leading to blindness due to several mutations in genes encoding for key proteins involved in the basic visual processes [1]
We developed a exible and thin retinal implant consisting of a multielectrode array approximately three times the size of the comparable epiretinal Argus II device and mounting 250 electrodes for epiretinal stimulation, which we called the very large array retinal stimulator (VLARS) [14]
The follow-up was conducted for 12 weeks, using slit lamp examination, funduscopy, ultrasound imaging, spectral domain optical coherence tomography (SD-OCT) and fundus photography
Summary
Retinitis pigmentosa (RP) is a retinal dystrophy leading to blindness due to several mutations in genes encoding for key proteins involved in the basic visual processes [1]. Through the course of the disease, photoreceptor cell degeneration leads to progressive visual impairment, neural cells of the inner retina remain functional [3, 4]. Targeting these cellular structures using retinal implant systems for electrical stimulation can restore meaningful visual perception in patients [5,6,7]. The currently available systems only restore a visual eld of approximately 10° visual angle requiring scanning of the area either with eye or head movements [13]. Acute stimulation experiments were performed to evaluate cortical responses induced by electrical stimulation of the retina
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