The very large electrode array for retinal stimulation (VLARS)—A concept study

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.

Photovoltaic retinal prosthesis restores high-resolution responses to single-pixel stimulation in blind retinas

“…New retinal prostheses should overcome this challenge and restore a large enough visual angle fitting the natural scanning via eye movements to provide a helpful and valuable visual aid to patients with retinitis pigmentosa. Wide-field retinal prostheses enabling theoretical visual angles larger than 30°were recently proposed and tested in preclinical studies to meet these requirements 11,30 .…”

In-Vivo Microsystems: A Review

“…Although this does not give a high-quality image, it does allow a blind person sufficient image quality to function and navigate around objects. This work has shown the feasibility of the approach, and work is continuing to improve the image quality [ 76 , 77 ], including increasing the area of the electrode array and increasing the density of electrodes [ 78 , 79 ]. Another approach is to implant arrays of the probe directly into the optical cortex at the back of the brain [ 80 ].…”

A machine-learning algorithm correctly classifies cortical evoked potentials from both natural retinal stimulation and electrical stimulation of the optic nerve

“…Previous studies pointed out that retinitis pigmentosa patients will benefit from the restoration of a wide visual angle [37,38]. Although some wide-field retinal prostheses are under development [5,[39][40][41][42], optic nerve's stimulation is attractive because its relatively small diameter facilitates the electrical stimulation of a wide visual field.…”