Chapter 1 - Restoring Vision to the Blind: The New Age of Implanted Visual Prostheses

Abstract

Of the many devices investigated, retina-based devices have shown the greatest success. These devices are limited, however, to eye diseases that destroy the photoreceptors but leave, at the very least, the ganglion cells intact for direct stimulation (Kellner, 2000). Of those diseases, retinitis pigmentosa (RP) has been the most attractive candidate because some affected individuals reach near-complete blindness at a relatively early age, and the inner (neural) retina is relatively spared. In comparison, age-related macular degeneration (AMD) has a late onset and does not cause total blindness for many years, typically leaving the retinal periphery functional. At present, there are seven major ongoing retinal prosthesis projects that have either implanted test subjects or have concrete plans to do so in the near future. The Argus II developed by Second Sight (Second Sight Medical Products, Lausanne, Switzerland) has been implanted during clinical trials in over 30 patients in both Europe and the United States (Humayun et al., 2012) where it has also been approved for commercial sale (in 2011 and 2013, respectively [Rizzo et al., 2014]). Currently, approximately 45 commercial devices have been implanted. In comparison, the Alpha-IMS system of Retina Implant AG has been implanted during clinical trials in over 40 patients (Zrenner, 2013) and in 2013 received CE (Conformité Européenne) approval for commercial sale in the European Union with the first sales expected in 2014 (W. Wrobel, personal communication,). In addition to these two commercial devices, the IRIS device developed by Intelligent Medical Implants (IMI) was implanted in 20 patients in 2003 and 2004 (Hornig et al., 2007). This IMI (Innovative Medicines Initiative) device has been acquired by Pixium, which is conducting renewed clinical trials. Furthermore, devices developed by the Bionic Vision Australia consortium (Saunders et al., 2014) the Boston Retina Implant Project (Rizzo, 2011), Nidek Co., Ltd. (Nidek Co., Aichi, Japan) (Fujikado et al., 2011), and the Stanford-based photovoltaic retinal prosthesis (PRIMA) (Mandel et al., 2013; Mathieson et al., 2012) have announced plans to enter clinical trials in the next few years. Functional results from some of these retinal implants will be discussed below. Recent Advances in Optic Nerve and Thalamic Stimulation Optic nerve stimulation seeks to create action potentials in the axons of the ganglion cells. Whereas epiretinal stimulation targets these ganglion cells at or very near their cell bodies in order to preserve retinotopy (Fried, Lasker,

What do blind people “see” with retinal prostheses? Observations and qualitative reports of epiretinal implant users

“…Because it is difficult to replicate biological infrastructure with microelectrode arrays, the goal has been to create a simplified visual signal that would provide some functional benefit for the recipient. Efforts to develop such a device have been undertaken by many groups over the past 50 years [1][2][3]. More recent efforts have focused on the retina, with three devices having achieved commercial approval to date.…”

Elektronische Netzhautimplantate – ein aufgegebener Traum?

“…Zunächst schätzen die meisten Patienten die Sehverbesserung durch die gegenwärtigen retinalen Implantate als zu gering für einen Nutzen im täglichen Leben ein [4,31,32]. Wie bereits präklinische Arbeiten zeigten [33], liegt das Auflösungsvermögen der gegenwärtigen Elektrodenkonfiguration des Retina Implant Alpha bei etwa 20/500 und bei Argus II bei 50/1200 und wird auch nur von wenigen Patienten erreicht.…”

“…Aktuell läuft eine erste Probandenstudie in Los Angeles und Houston (ClinicalTrials.gov Identifier: NCT03344848) [41]. Allerdings haben alle Ansätze zu kortikalen Prothesen bisher keine dauerhaften Seheindrücke vermitteln können [4,31,32]. Ein weiterer neuartiger kortikaler Ansatz, bei dem mehrere 16-Kanal-Nadelelektrodenfelder mit drahtloser Energie und Signalübertragung in Area V1 eingesetzt werden (ICVP-Implantate), steht kurz vor der klinischen Anwendung [42].…”

What do blind people “see” with retinal prostheses? Observations and qualitative reports of epiretinal implant users

“…Because it is difficult to replicate biological infrastructure with microelectrode arrays, the goal has been to create a simplified visual signal that would provide some functional benefit for the recipient. Efforts to develop such a device have been undertaken by many groups over the past 50 years [1–3]. More recent efforts have focused on the retina, with three devices having achieved commercial approval to date.…”