One of the major causes for blindness in the Western world is degenerative diseases of the outer retina. Such diseases causes the body’s natural light receptors to malfunction and can lead to visual impairment and blindness. Scientists at the Technion have recently developed a method to restore eye sight by projecting holographic images directly on to the retina.
In other recent studies, people suffering from such conditions were able to regain some of their eyesight using implants that generate electric stimulation. However, in order to get better results, individual stimulation of cells is needed.
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“Restoring lost vision to basic functionality levels has become possible recently through invasive surgical insertion of artificial electronic implants that electrically stimulate surviving retina cells, similar to the snail-shaped cochlear implants used to treat the hearing impaired,” says Professor Shy Shoham from the Faculty of Biomedical Engineering at the Technion. “Our approach is different and attempts to stimulate the surviving retinal cells without the need for direct implants onto the retina, and may eventually make surgery and implants redundant.”
Combining genetics with holographic projection
This recent research is based on a combination of holography and optogenetics. “Our optogenetic approach relies on genetic expression of ion channels that are light sensitive (proteins derived from algae) in the ganglion cells of the retina,” explains Dr. Inna Reutsky-Gefen. Basically, the researchers used genetics to turn ganglion cells that are naturally transparent, into light sensors.
After the genetic modification is made, when holographic images are projected onto the damaged retina, the brain deciphers them the same way it would a sight captured by a fully functioning retina. The projection method in the experiment uses a technique called diffractive spatial light modulation, which requires relatively little energy. This way, it will be possible in the future to mount such a device on an external frame (such as glasses) as a portable component of a retinal “prosthetic” system.
“Applications of this approach are not limited to vision restoration,” stresses Shoham. “Holographic stimulation strategies can permit flexible control of the activity of large cellular networks which artificially express light-sensitive channels, and pave the way towards new medical devices and scientific tools that can help “break” the brain’s neural code.”
Shoham and Reutsky-Gefen’s study is published in the multidisciplinary Journal, Nature Communications, co-authored by Lior Golan, Dr. Nairouz Farah, Adi Schejter, Limor Tsur, and Dr. Inbar Brosh. The research was funded by a European Research Council Starting Grant to Prof. Shoham.
Photo: Inna Gefen, Roman Kanevsky and Shy Shoham (courtesy)