Supplementary Material for: Extraction of a Chronically Implanted, Microfabricated, Subretinal Electrode Array

Purpose: To assess the feasibility of extraction of a chronically implanted subretinal electrode array. Methods: Inactive, polyimide strips (10 mm × 1.5 mm × 15 μm) were surgically implanted into the subretinal space of 8 rabbits using a mostly ab externo approach. Pre- and postoperative clinical examinations, electroretinography and in some cases optical coherence tomography were performed to follow the course of the eyes. Two months after implantation, the polyimide strips were extracted from 5 eyes; 2 animals kept the implants and served as controls. All animals were then sacrificed and eyes enucleated for histological examination. Results: All 8 surgeries yielded successful placement of the arrays into the subretinal space. All 5 extraction surgeries were performed without obvious complications. Clinical examinations and electroretinography did not reveal any significant abnormalities. The histological examinations showed alterations from normal anatomy in all animals; the anatomical changes in the explanted animals were relatively mild and confined to the area of the surgery. Conclusions: Successful extraction of electrode arrays from the subretinal space of rabbits can be reliably performed 2 months after implantation, which is beyond the time period when postoperative scarring would be most intense.