Advances and challenges in the development of visual prostheses

Abstract

The past 20 years have witnessed significant advancements in the field of visual prostheses, with developments spanning from early retinal implants to recent cortical approaches.This Perspective looks at some of the remaining challenges to achieve the ambitious clinical goals that these technologies could enable.Visual impairment profoundly impacts individuals' lives, compromising personal autonomy and diminishing overall quality of life.Over the last 2 decades, the field has progressed from experimental concepts to clinically available devices [1].This evolution has yielded varying degrees of success, reflecting both advances made and the challenges that remain.The early 2000s marked the beginning of tangible progress in visual prostheses development, particularly with the emergence of retinal implants.The Argus II Retinal Prosthesis System, developed by Second Sight, was one of the first devices to receive regulatory approval [2].The Alpha IMS developed by Retina Implant AG also made significant strides [3].These early systems provided users with a limited form of vision, allowing them to perceive light, shapes, and motion.However, despite the initial promising results, the devices ultimately fell short of unmet expectations, leading to their eventual withdrawal from the market [4].This outcome underscores the complexity of developing visual prostheses and highlights the need for continued research and development in the field.Many of the challenges in the field of visual prostheses are shared with the broader field of neurotechnology and span various aspects of neural interface development and implementation, reflecting the interconnected nature of neuroscientific research and technological innovation [5].To be able to stimulate individual neurons, the microelectrodes should be located very close to target cells and have dimensions similar to the neurons they are trying to stimulate.Likewise, both the electrodes and the substrates housing the connecting pathways must be highly biocompatible and completely insulated.This is crucial to mitigate the foreign body response, prevent degradation, and minimize crosstalk between electrodes.Furthermore, it is important to ensure the mechanical stability of implanted devices over time.Additionally, a significant challenge is the limited ability of current devices to constrain electrical fields to target specific cell types or structures.All these requirements impose unique constraints on the architecture and materials used in the design and implementation of visual prostheses.