Development of Polyimide Photodiode Electrode Array System for Laser-Signaling Retinal Prosthesis

Abstract

Abstract: : Purpose: To develop safe, inexpensive and efficient retinal prosthesis, silicon retinal tack and Vertical Cavity Surface Emitting Laser (VCSEL) signal transducer were designed, flexible polyimide electrode array was made and biocompatibility was evaluated. Methods: Using silicon micromachining technology, based on semiconductor manufacturing, retinal tack was made and implanted in rabbit eyes. VCSEL was selected as laser source with simulated by ray tracing technique with point spread function. Triangular flexible polyimide electrode array was made based on semiconductor manufacturing. The in vitro biocompatibility of polyimide electrode array was tested by co-culture with human retinal pigment epithelial cells, monitoring cell morphology and survival. In vivo biocompatibility was also checked by implanting it in the rabbit eyeball. Inflammatory reaction and histological change of eye were evaluated. Impedance of each electrode was also tested. Results: The silicon microtack was fabricated without difficulties and also fixed easily in the rabbit eyeball and showed stable function. VCSEL exhibited good focusing characteristics on simulation. Polyimide electrode array showed good biocompatibility in vitro culture test for 4 weeks and there was no inflammatory change in rabbit retina for more than 2 months. It also showed even impedance between each electrode. Electroretinogram showed no difference between operated eye and control eye. Conclusion: Silicon retinal tack can be used in retinal stimulator fixation and polyimide photoelectrode array with VCSEL system can be a promising candidate for retinal prosthesis.

Keywords: 607 transplantation • 554 retina • 485 neuro-ophthalmology: cortical function/rehabilitation