Improved version

Worldwide, 32 million people are blind, up to 4 million of them suffer due to the loss of light-sensitive cells in the retina. The most promising method of treating this type of blindness is a retinal implant containing electrodes that stimulate retinal cells. Unfortunately, modern implants give very poor results, and their owners are still considered blind. In order to lead a normal life, the patient must restore a field of vision of at least 40 degrees along all axes. Modern implants give only 20 degrees.

Diego Gezzi, head of the Department of Neuroengineering (LNE) Medtronic at the EPFL School of Engineering, and his colleagues came up with a wireless implant made of flexible and malleable material containing photovoltaic pixels. It is expected to give users a field of view of up to 46 degrees and provide much better resolution.

Disadvantages of existing implants

Currently available retinal implants consist of a grid of electrodes placed directly on the retina. They are connected to glasses and a camera, as well as to a portable microcomputer. The camera captures images that fall into the patient's field of vision and sends them to a computer, which turns them into electrical signals and transmits them to the electrodes. The electrodes stimulate the retinal ganglion cells, creating light patterns. The implantable must learn to interpret incoming visual sensations in order to "see" the images. The more numerous and detailed the patterns, the easier it is to recognize them.

The wider the surface, the more pixels

The new implant from EPFL researchers, like conventional implants, consists of an array of pixels, glasses and a camera, but has no wires.

Drawings from the EPFL press release.

It also has a large surface area, allowing you to increase the number of photovoltaic pixels and expand the field of view. The larger size means that photovoltaic pixels will stimulate more retinal cells. Existing implants stimulate cells only in its center.

The same image looks different depending on the number of pixels available. Here there are from 60 to the unattainable 20,000, in the prototype POLYRETINA – 2215, as in the second right pictures.

Surgical limitations

Until now, the size of retinal implants has been limited mainly by the length of the surgical incision in the eye, which should be as small as possible so as not to damage the tissue. To overcome this obstacle, the researchers decided to work with a particularly flexible material that will allow the implant to be folded during surgery and installed in the eye without the need to enlarge the incision. The implant is made of a transparent non-toxic polymer that is already used in medicine.

Photovoltaic pixels and no wires

The researchers were able to make the implant wireless by replacing the electrodes with photovoltaic pixels. Unlike electrodes, solar-powered pixels generate electric current themselves and do not require an external energy source. Therefore, the light captured by the camera no longer needs to be converted into electrical signals, instead it needs to be amplified so that photovoltaic pixels can function.

Pixels will only respond to light signals that correspond to certain parameters of intensity, duration and wavelength. Another advantage of photovoltaic pixels is that they take up less space than electrodes, and more of them can fit on the implant, which will further increase visual acuity and expand the field of vision.

In the tests conducted on a plastic model of the human eye, the prototype showed safety and successfully increased the field and visual acuity. The next step is planned in vivo studies to study other factors, for example, the behavior of pixels in the eye and the life of the implant. It will also be interesting to see how well animals and humans adapt to this new way of seeing, which is different from our natural vision.

Article by L. Ferlauto et al. Design and validation of a foldable and photovoltaic wide-field epiretinal prosthesis is published in the journal Nature Communications.

Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru according to EPFL materials: A retinal implant that is more effective against blindness.