Bionic eye promises a brighter future

Dr. Yossi Mandel, Head of the Ophthalmic Science and Engineering Lab at Bar Ilan, is advancing breakthrough retinal prosthesis technology to restore the sight of patients with severely impaired vision. Funded by the prestigious ERC Starting Grant, Mandel’s cross-disciplinary team is devising a hybrid retinal implant that stimulates live neural cells to send visual information to the brain.

Six million dollar man

Some of us still recall the epic TV series from the 70s The 6 Million Dollar Man, with Colonel Steve Austin who, after a severe injury had several organs including his eye, replaced with bionic implants that enhanced his strength, speed and vision far above human norms. But, what was once the domain of science fiction, is inching closer to becoming an everyday reality for more than 200 million people worldwide living with moderate to severe vision impairment.

Dr. Yossi Mandel is a senior lecturer at the Faculty of Life Sciences at Bar Ilan, and a certified ophthalmic surgeon with a PhD in Bioengineering. He conducts cutting-edge research on two main diseases that cause loss of vision: Retinitis pigmentosa (a genetic disorder) and AMD (Age-related macular degeneration) – the most common cause of blindness in the Western world.

“The eye is like a sophisticated camera integrated in an image-processing computer”, said Mandel. “Its main component, the retina, contains light-sensitive cells with advanced image-processing capabilities. These cells are arranged in distinct layers: The photoreceptor cells which convert the light into a neuronal signal; the bipolar cells which process this information and pass it on to the third layer– the Ganglion cells–where data is further processed, digitized and transmitted to the brain, which enables us to see”, he explained.

Hybrid retinal implant

To emulate the retina’s intricate capabilities, the implant contains tiny electrodes which replace the natural photoreceptors. The electrodes are integrated in live functioning neural cells, which are intended to stimulate the neurons to send visual information to the brain. “Neuronal stimulation is achieved in a more natural way than other existing prosthetic devices that use direct electrical activation”, Mandel pointed out. “There is already an FDA-approved artificial retinal prosthesis that is used for treating these diseases, though it has shown only limited results due to the large spaces between the electrodes and the neurons”, he said. Despite their debilitating outcomes, the diseases mentioned above affect mainly the photoreceptors, while the other layers remain relatively functional. To restore lost sight of blind patients, Mandel is developing a hybrid retinal chip which will be implanted in their retinas.

Now, the team is engineering highly specific neural cells from human embryonic stem cells, stained with special dyes that track their activity, and embedded in the electrodes. “We expect that if these cells respond to electricity in a similar way as nerve cells, they will release glutamate, which the cells use for neural signalling. These signals travel within the retina, and through the optic nerve to the brain, and serve as the basis for visual perception”, he said.

This technology requires the combined efforts of experts in nanotechnology, ophthalmology, bio-electricity, neuron engineering, stem cell research, and materials science.

Mandel added that the challenge is in carefully engineering live cells without affecting their function. “If we succeed, in the future we might enable higher, near-natural vision sharpness−up to 100 times better than what has been achieved until now”, he stated.

Combining bionic vision with natural vision

Dr. Mandel, together with Prof. Daniel Palanker from the Department of Ophthalmology at Stanford University are collaborating in a research project studying a retinal prosthetic chip. The device is intended to enable bionic vision in patients with some eyesight. It stimulates any remaining natural vision, and will function as an integral part of the eye.

The chip was implanted in rats’ eyes. To artificially stimulate the retina, the team engineered a head-mounted image-projection system using NIR (near infrared) laser pulses which included a miniature Digital Mirror Device (DMD) with a periscope relay lens. This enabled the projection of complex retinal stimulation patterns directly onto the animal’s retina.

“We are studying how the brain responds to stimuli of the prosthetic implant, in order to find out whether the brain will integrate it into natural vision in healthy parts of the retina”, Mandel said.

Mandel explained that this is exactly what occurs in AMD patients, whereby the center of the retina is damaged, but the peripheral retina is healthy. For these patients, implanting this chip in the center of the retina provides them with two visual systems: central prosthetic vision and peripheral normal vision. Several patients in Europe and in the U.S. have already been implanted with these tiny 2-mm sized devices, aimed at restoring vision in the central vision field.

Drug-delivering nano eye drops 

Mandel has also partnered with Prof. Itamar Willner from the Institute of Chemistry at the Hebrew University of Jerusalem. They have developed unique nanoparticles that could be added to eye drops for depositing drugs into the eye.

To measure the efficacy of penetration of the drops in the eye, and to test various possible drugs, they created a rat model of a retinal disease similar to AMD. They hope that in the future, this could eliminate the need for AMD patients to receive repeated eye injections of the anti-VEGF (anti vascular endothelial growth factor) drug that reduces blood vessel growth or swelling.