Surgical Guides for Electrode Array Implantation Into the Subretinal Space

Abstract

Abstract: : Purpose: To develop and fabricate prototype surgical guides (SG) with various features that will improve the technique by which an electrode array (EA) is introduced into the sub–retinal space during the implantation of an ab–externo retinal prosthesis. The hypothesis was that a SG could perform several functions including create a path for the EA, create a sub–retinal bleb during SG insertion with an integrated fluidic channel, hold the EA and release once insertion is complete with an integrated vacuum port. Methods: Several prototype guides with different features were fabricated to assess the usefulness of the following features: 1) a ‘J–bend’ in the edge of the SG to capture and direct one edge of the EA during insertion, 2) a fluidic channel to utilize hydraulic pressure to create a bleb around the SG during insertion, 3) a vacuum port to hold the EA to the SG during insertion. SGs with these features, and combinations thereof, were manually fabricated. The J–bend was fashioned by crimping the edge of a guide into a very tight bend. The fluid channel and vacuum port were formed by sandwiching a small bore polyimide tubing between two sheets of polyimide. The fluid channel tube extended to the tip of the SG while the vacuum port tube extended only to a small hole through one polyimide sheet near the SG tip. Though other methods of bonding the sheets together were tested, the best results were obtained by using polyimide tape as one of the sheets. Bonding was not perfect, but results were acceptable for testing. Silicone tubing was used to step up to a size attachable to a fluid delivery system. The SGs were hand cut and the tips were thinned and rounded by hand polishing. The various prototype guide configurations were then tested in mock implant experiments. Results: Prototype SGs with various features were successfully hand fabricated. The SGs, though unrefined, were tested surgically with mixed results. The fluidic channel has demonstrated some success, but early successes have been limited by tubing leaks. More experiments are planned with resealed tubing. Conclusions: Prototype SGs can be successfully fabricated with various features. Though some mock implant experiments have been successful, more are planned to determine the true potential of properly designed and fabricated SGs in placing an EA into the sub–retinal space during the implantation of an ab–externo retinal prosthesis.

Keywords: age-related macular degeneration • retinal degenerations: hereditary • retina