A Visionary Breakthrough

For decades, retinal implants have been one of the greatest hopes for patients with degenerative blindness. Yet despite technological progress, their effectiveness has remained limited.

Current implants deliver very low spatial resolution, providing visual acuity ranging from 20/440 to 20/1200. Far from natural sight. Clinical trials have shown patients can use these devices to read large text with magnification, recognize signs, and improve functional vision. Still, contrast sensitivity and fine details remain out of reach, and computational models suggest the ceiling of existing technology is around 20/100 at best.

Another critical challenge lies in how current implants stimulate the retina: with non-selective, pulsed electrical signals that activate all cells simultaneously. In contrast, natural vision selectively engages different retinal cells in response to changes in light intensity, creating the dynamic richness of healthy sight.

The Hybrid Solution: Where Engineering Meets Biology

Prof. Yossi Mandel, head of the Ophthalmic Science and Engineering Lab at Bar-Ilan University, together with his team and collaborators including Prof. Zeev Zalevsky of BIU’s Faculty of Engineering, has developed a hybrid retinal implant that could overcome these barriers. Their study, published in Advanced Functional Materials, introduces an implant that integrates two powerful components:

• High-density microelectrodes engineered in a unique 3D “microwell” design.
• Glutamatergic neurons, derived from embryonic stem cells, capable of maturing into young photoreceptors.

Each microwell is 10 microns wide and up to 15 microns deep, housing a single neuron. At the base of every well sits a microelectrode just 5–6 microns in diameter. This intimate coupling increases the local electric field by a factor of 1,000 compared to flat electrodes.

Results: Sharper, Selective, and More Natural Vision

The novel structure produced dramatic results:

• Ultra-low activation thresholds—comparable to intracellular stimulation, hundreds of times lower than in existing implants.
• Powerful neuronal responses—a single cell reacted to minimal stimulation (just five picocoulombs), generating a membrane change of 18 millivolts—ten times stronger than a photoreceptor’s natural response to light.
• Minimal signal “crosstalk”—the microwell design reduced unwanted activation of neighboring cells by a factor of 1:430, enabling sharp contrast and clearer vision.

At BIU’s Institute of Nanotechnology and Advanced Materials (BINA), the team fabricated the device and validated it through experiments. Stem-cell-derived neurons seeded into the microwells not only survived at high rates but also extended axonal projections toward the host retina. Importantly, the presence of synaptic markers (Ribeye) suggested the formation of active biological connections between implanted and host retinal cells.

A Glimpse Into the Future of Vision Restoration

This breakthrough marks the first demonstration of a bioengineered synaptic interface between microelectronic implants and biological neurons designed to “translate” electrical stimulation into the retina’s natural language.

Prof. Mandel explains:
“Our goal is to move beyond the limits of pure electronics. By integrating living neurons with microelectrode arrays, we are creating an implant that not only stimulates the retina but does so in a biologically meaningful way. The hope is to provide blind patients with vision that is sharper, clearer, and closer to natural sight than ever before.”

The hybrid retinal implant is now advancing toward further preclinical testing in models of retinal degeneration, with the long-term goal of enabling human trials.

Collaboration Across Disciplines

The project was a joint effort of researchers from BIU’s Faculty of Life Sciences, Faculty of Engineering, and BINA Nanotechnology Institute. Alongside Prof. Mandel and Prof. Zalevsky, contributors included Dr. Nairoz Farah, Dr. Amos Markus, doctoral student Gal Shafon, and Dr. Yoav Shemla, among others.