Chapter 5: Emerging Biomaterials for Retinal Implants Check Access

Retinal neurodegenerative diseases cause debilitating and profound vision loss that impacts millions of individuals. To treat such diseases, significant multidisciplinary research and developmentary effort have been dedicated toward realising a functional visual prosthesis, a bionic eye. The first generation of these bionic eyes (or retinal prostheses) successfully demonstrated elicitation of visual percepts and restoration of basic visual function in severely visually impaired patients by electrically stimulating surviving neurons. However, the experience for most implant recipients has been largely underwhelming, limiting clinical adoption, and leading to multiple commercial withdrawals. The next generation of bionic eyes seeks to fulfil practical vision requirements by offering greater visual coverage, higher pixel resolution, and more biocompatible neural interfacing. This requires a large, flexible prosthesis with numerous, dense electrodes in stable contact with retinal tissue, imposing immense biomaterial and engineering challenges for which conventional materials like metals and silicon electronics exhibit fundamental limitations. This has led to the investigation of novel biomaterials including liquid crystal polymers, organic conducting polymers, nanomaterials, diamond, and hydrogels. Proof-of-concept studies involving these biomaterials have promisingly demonstrated improved performance characteristics and successful integration into prototype retinal prostheses. However, a notable absence of chronic in vivo studies prevents the adoption and in-human testing of many such emerging biomaterials.