Implantation of multiple suprachoroidal electrode arrays in rabbits

Abstract

Purpose: Epiretinal and subretinal prosthesis have been shown to be a valid way to provide some vision to patients with advanced outer retinal degeneration and profound vision loss. However, the field of vision for these patients is markedly limited by the area occupied by the electrode array. In this study, we aimed to evaluate the feasibility of implantation of multiple suprachoroidal electrode arrays in a single eye in order to increase the field of vision in patients implanted with retinal prosthesis.

Methods: The right eye of seventeen Dutch rabbits (age range, 5-6 months) was used for the study. Multiple inactive custom-made electrode arrays were inserted into the suprachoroidal space (SCS) and animals were followed up for up to 6 months using fundus photography, optical coherence tomography (OCT), and fluorescein angiography (FA).

Results: It was possible to surgically implant up to 8 electrode arrays in a single eye. None of the rabbits showed any major complications. The electrodes were well tolerated and remained in position in all rabbits. There was no evidence of retinal damage on follow-up exams and FA throughout the study.

Conclusion: Multiple suprachoroidal electrode array implantation is feasible and may provide a novel approach to increase the field of vision in subjects implanted with retinal prosthesis.

Keywords: Array; Electrodes; Retinal implant; Retinal prosthesis; Suprachoroidal.

Fig. 1

Suprachoroidal electrode array. Left: Schematic illustration of the posterior segment of a rabbit eye with 4 electrode arrays in 4 different quadrants. Right: Microphotograph of the electrode array.

Fig. 2

Fundus photography of rabbit eye with implanted electrode arrays. Color fundus photograph (Left) and fluorescein angiography (FA) (Right) of the right eye of an albino rabbit showing 2 adjacent electrode arrays (indicated by the white arrows). Note difficulty of seeing electrode arrays on fluorescein angiogram and lack of any staining or leakage in the late phase.

Fig. 3

Fundus imaging of rabbit eyes with implanted electrode arrays. Optical coherence tomography (OCT) of the right eye of 2 rabbits (Top Left, Top Right) with the corresponding fundus picture (Bottom Left, Bottom Right). White arrows on the fundus pictures show adjacent electrode arrays. Yellow arrows show the electrode array on the OCT images located between the choroid and sclera. Hyperreflective spots (orange arrows) show individual electrodes.