Surgical Implantation of Different Geometries of Electrode Arrays in Minipig Eyes

Abstract

Purpose: : This work is related to the efforts of the Boston Retinal Implant Project to develop a sub-retinal prosthesis to restore vision to the blind. The specific purpose of this presentation summarizes the surgical results of implantation of different electrode arrays in Yucatan minipig eyes.

Methods: : 3 different geometries of inactive, polyimide electrode arrays were implanted into 13 minipig eyes via an ab externo method to study stimulation and biocompatibility. Typical arrays were 1.510 mm x 101.5 mm x 15 µm, each with 15 Iridium Oxide electrodes (400 micron diameter). Larger arrays were 16 microns thick, each with 100 Iridium Oxide electrodes (200 micron diameter). Pillar arrays consisted of a flexible polyimide base with 70 micron-tall, SU8 pillars of various diameters ranging from 10 - 80 microns. To prevent excessive bleeding during surgery, "controlled" systemic hypotension (30 - 45 mmHg) was maintained. After partial vitrectomy, a local retinal detachment was created underneath the flap by sub-retinal injection of BSS® and Healon®. The typical arrays were placed just temporal to the center of the retina. Large arrays required larger scleral flap and retinal detachment and were placed peripherally.

Results: : 13 electrode arrays were successfully implanted into subretinal space of 13 Yucatan minipig eyes. Retinal incarceration happened during one survival large array implantation surgery. No other surgical complications were observed. Our success-rate of implantation surgeries without severe complications on minipig eyes is > 90%. This compares very favorably with our results prior to using hypotensive anesthesia and Healon® when the implantation was successful in 5 of the 18 implantation surgeries on minipig eyes.

Conclusions: : After using nitroprusside to control bleeding and Healon® to maintain the retinal detachment, our surgical results have been greatly improved. Typical arrays, pillar arrays and large arrays can be safely implanted into subretinal space with our ab externo methods.

Keywords: retina • retina: proximal (bipolar, amacrine, and ganglion cells) • age-related macular degeneration