Beyond the retina

An international consortium of physicians and technological researchers called CU-AGAIN are in the process of developing a device that will transmit visual information through an array electrodes inserted directly into the optic nerve, said Stanislao Rizzo MD, at the 15th EURETINA Congress in Nice. “The stimulation of the optic nerve will allow the treatment of a variety of hereditary or acquired forms of blindness, potentially targeting patients who are not suitable for retinal prostheses,” said Dr Rizzo, University of Florence, who is participating in the project, but has no financial interest in it. Those involved in the project include a team at the London City College who have developed a prototype implantable optic nerve stimulator, a team from the Ecole Polytechnique Federale de Lausanne, who are coordinating the project and are in charge of system integration and testing, a team at the University of Pisa, who will the handle micro-fabrication of the implant, and a team at Correggio University Hospital who will develop the surgery. “CU-Again will establish a proof of principle for the use of self opening extramural electrode arrays implanted in an intracranial or intra-orbital position of the optic nerve to provide large field high resolution vision,” said Dr Rizzo. He explained further that their aim is to create a successful neural interface that can selectively stimulate or record neural signals from small groups of axons without causing significant neural damage and remaining actively stable over time. IMPLANT DESIGN Their implant design is based on the experimental SELINE device, a three-dimensional electrode array designed to be transversely or obliquely inserted into nervous tissue. Research has shown that it can allow simultaneous stimulation from different fascicles innervating separate peripheral targets. “The three-dimensional electrode provides an effective anchorage system to nervous tissue that can improve the stability of the implant,” Dr Rizzo added. The adaptation of that design to the optic nerve involves two basic concepts. The first is to take advantage of the space compression of the optic nerve and induce recovery of a wide field, high resolution vision with a single implant. The second concept is to create a controller system to adjust the parameters depending on the detected visual responses, thus allowing the calibration of the device. So far the CU-Again team have developed a prototype implant and, at the time of this presentation were in the process of developing a neuromorphic video encoder for the device. Experimental validation and animal and clinical testing will follow. Stanislao Rizzo: Stanislao.rizzo@gmail.com