Tag Archives: retinal prosthesis

A new class of artificial retina

If I read the news release rightly (keep scrolling), this particular artificial retina does not require a device outside the body (e.g. specially developed eyeglasses) to capture an image to be transmitted to the implant. This new artificial retina captures the image directly.

The announcement of a new artificial retina is made in a March 13, 2017 news item on Nanowerk (Note: A link has been removed),

A team of engineers at the University of California San Diego and La Jolla-based startup Nanovision Biosciences Inc. have developed the nanotechnology and wireless electronics for a new type of retinal prosthesis that brings research a step closer to restoring the ability of neurons in the retina to respond to light. The researchers demonstrated this response to light in a rat retina interfacing with a prototype of the device in vitro.

They detail their work in a recent issue of the Journal of Neural Engineering (“Towards high-resolution retinal prostheses with direct optical addressing and inductive telemetry”). The technology could help tens of millions of people worldwide suffering from neurodegenerative diseases that affect eyesight, including macular degeneration, retinitis pigmentosa and loss of vision due to diabetes

Caption: These are primary cortical neurons cultured on the surface of an array of optoelectronic nanowires. Here a neuron is pulling the nanowires, indicating the the cell is doing well on this material. Credit: UC San Diego

A March 13, 2017 University of California at San Diego (UCSD) news release (also on EurekAlert) by Ioana Patringenaru, which originated the news item, details the new approach,

Despite tremendous advances in the development of retinal prostheses over the past two decades, the performance of devices currently on the market to help the blind regain functional vision is still severely limited–well under the acuity threshold of 20/200 that defines legal blindness.

“We want to create a new class of devices with drastically improved capabilities to help people with impaired vision,” said Gabriel A. Silva, one of the senior authors of the work and professor in bioengineering and ophthalmology at UC San Diego. Silva also is one of the original founders of Nanovision.

The new prosthesis relies on two groundbreaking technologies. One consists of arrays of silicon nanowires that simultaneously sense light and electrically stimulate the retina accordingly. The nanowires give the prosthesis higher resolution than anything achieved by other devices–closer to the dense spacing of photoreceptors in the human retina. The other breakthrough is a wireless device that can transmit power and data to the nanowires over the same wireless link at record speed and energy efficiency.

One of the main differences between the researchers’ prototype and existing retinal prostheses is that the new system does not require a vision sensor outside of the eye [emphasis mine] to capture a visual scene and then transform it into alternating signals to sequentially stimulate retinal neurons. Instead, the silicon nanowires mimic the retina’s light-sensing cones and rods to directly stimulate retinal cells. Nanowires are bundled into a grid of electrodes, directly activated by light and powered by a single wireless electrical signal. This direct and local translation of incident light into electrical stimulation makes for a much simpler–and scalable–architecture for the prosthesis.

The power provided to the nanowires from the single wireless electrical signal gives the light-activated electrodes their high sensitivity while also controlling the timing of stimulation.

“To restore functional vision, it is critical that the neural interface matches the resolution and sensitivity of the human retina,” said Gert Cauwenberghs, a professor of bioengineering at the Jacobs School of Engineering at UC San Diego and the paper’s senior author.

Wireless telemetry system

Power is delivered wirelessly, from outside the body to the implant, through an inductive powering telemetry system developed by a team led by Cauwenberghs.

The device is highly energy efficient because it minimizes energy losses in wireless power and data transmission and in the stimulation process, recycling electrostatic energy circulating within the inductive resonant tank, and between capacitance on the electrodes and the resonant tank. Up to 90 percent of the energy transmitted is actually delivered and used for stimulation, which means less RF wireless power emitting radiation in the transmission, and less heating of the surrounding tissue from dissipated power.

The telemetry system is capable of transmitting both power and data over a single pair of inductive coils, one emitting from outside the body, and another on the receiving side in the eye. The link can send and receive one bit of data for every two cycles of the 13.56 megahertz RF signal; other two-coil systems need at least 5 cycles for every bit transmitted.

Proof-of-concept test

For proof-of-concept, the researchers inserted the wirelessly powered nanowire array beneath a transgenic rat retina with rhodopsin P23H knock-in retinal degeneration. The degenerated retina interfaced in vitro with a microelectrode array for recording extracellular neural action potentials (electrical “spikes” from neural activity).

The horizontal and bipolar neurons fired action potentials preferentially when the prosthesis was exposed to a combination of light and electrical potential–and were silent when either light or electrical bias was absent, confirming the light-activated and voltage-controlled responsivity of the nanowire array.

The wireless nanowire array device is the result of a collaboration between a multidisciplinary team led by Cauwenberghs, Silva and William R. Freeman, director of the Jacobs Retina Center at UC San Diego, UC San Diego electrical engineering professor Yu-Hwa Lo and Nanovision Biosciences.

A path to clinical translation

Freeman, Silva and Scott Thorogood, have co-founded La Jolla-based Nanovision Biosciences, a partner in this study, to further develop and translate the technology into clinical use, with the goal of restoring functional vision in patients with severe retinal degeneration. Animal tests with the device are in progress, with clinical trials following.

“We have made rapid progress with the development of the world’s first nanoengineered retinal prosthesis as a result of the unique partnership we have developed with the team at UC San Diego,” said Thorogood, who is the CEO of Nanovision Biosciences.

Here’s a link to and a citation for the paper,

Towards high-resolution retinal prostheses with direct optical addressing and inductive telemetry by Sohmyung Ha, Massoud L Khraiche, Abraham Akinin, Yi Jing, Samir Damle, Yanjin Kuang, Sue Bauchner, Yu-Hwa Lo, William R Freeman, Gabriel A Silva.Journal of Neural Engineering, Volume 13, Number 5 DOI: https://doi.org/10.1088/1741-2560/13/5/056008

Published 16 August 2016 • © 2016 IOP Publishing Ltd

I’m not sure why they waited so long to make the announcement but, in any event, this paper is behind a paywall.

Improving the quality of sight in artificial retinas

Researchers at France’s Centre national de la recherche scientifique (CNRS) and elsewhere have taken a step forward to improving sight derived from artificial retinas according to an Aug. 25, 2016 news item on Nanowerk (Note: A link has been removed),

A major therapeutic challenge, the retinal prostheses that have been under development during the past ten years can enable some blind subjects to perceive light signals, but the image thus restored is still far from being clear. By comparing in rodents the activity of the visual cortex generated artificially by implants against that produced by “natural sight”, scientists from CNRS, CEA [Commissariat à l’énergie atomique et aux énergies alternatives is the French Alternative Energies and Atomic Energy Commission], INSERM [Institut national de la santé et de la recherche médicale is the French National Institute of Health and Medical Research], AP-HM [Assistance Publique – Hôpitaux de Marseille] and Aix-Marseille Université identified two factors that limit the resolution of prostheses.

Based on these findings, they were able to improve the precision of prosthetic activation. These multidisciplinary efforts, published on 23 August 2016 in eLife (“Probing the functional impact of sub-retinal prosthesis”), thus open the way towards further advances in retinal prostheses that will enhance the quality of life of implanted patients.

An Aug. 24, 2015 CNRS press release, which originated the news item, expands on the theme,

A retinal prosthesis comprises three elements: a camera (inserted in the patient’s spectacles), an electronic microcircuit (which transforms data from the camera into an electrical signal) and a matrix of microscopic electrodes (implanted in the eye in contact with the retina). This prosthesis replaces the photoreceptor cells of the retina: like them, it converts visual information into electrical signals which are then transmitted to the brain via the optic nerve. It can treat blindness caused by a degeneration of retinal photoreceptors, on condition that the optical nerve has remained functional1. Equipped with these implants, patients who were totally blind can recover visual perceptions in the form of light spots, or phosphenes.  Unfortunately, at present, the light signals perceived are not clear enough to recognize faces, read or move about independently.

To understand the resolution limits of the image generated by the prosthesis, and to find ways of optimizing the system, the scientists carried out a large-scale experiment on rodents.  By combining their skills in ophthalmology and the physiology of vision, they compared the response of the visual system of rodents to both natural visual stimuli and those generated by the prosthesis.

Their work showed that the prosthesis activated the visual cortex of the rodent in the correct position and at ranges comparable to those obtained under natural conditions.  However, the extent of the activation was much too great, and its shape was much too elongated.  This deformation was due to two separate phenomena observed at the level of the electrode matrix. Firstly, the scientists observed excessive electrical diffusion: the thin layer of liquid situated between the electrode and the retina passively diffused the electrical stimulus to neighboring nerve cells. And secondly, they detected the unwanted activation of retinal fibers situated close to the cells targeted for stimulation.

Armed with these findings, the scientists were able to improve the properties of the interface between the prosthesis and retina, with the help of specialists in interface physics.  Together, they were able to generate less diffuse currents and significantly improve artificial activation, and hence the performance of the prosthesis.

This lengthy study, because of the range of parameters covered (to study the different positions, types and intensities of signals) and the surgical problems encountered (in inserting the implant and recording the images generated in the animal’s brain) has nevertheless opened the way towards making promising improvements to retinal prostheses for humans.

This work was carried out by scientists from the Institut de Neurosciences de la Timone (CNRS/AMU) and AP-HM, in collaboration with CEA-Leti and the Institut de la Vision (CNRS/Inserm/UPMC).

Artificial retinas


© F. Chavane & S. Roux.

Activation (colored circles at the level of the visual cortex) of the visual system by prosthetic stimulation (in the middle, in red, the insert shows an image of an implanted prosthesis) is greater and more elongated than the activation achieved under natural stimulation (on the left, in yellow). Using a protocol to adapt stimulation (on the right, in green), the size and shape of the activation can be controlled and are more similar to natural visual activation (yellow).


Here’s a link to and a citation for the paper,

Probing the functional impact of sub-retinal prosthesis by Sébastien Roux, Frédéric Matonti, Florent Dupont, Louis Hoffart, Sylvain Takerkart, Serge Picaud, Pascale Pham, and Frédéric Chavane. eLife 2016;5:e12687 DOI: http://dx.doi.org/10.7554/eLife.12687 Published August 23, 2016

This paper appears to be open access.