Title: Prosthetic vision with a photovoltaic substitute for the lost photoreceptors
Abstract: Retinal degenerative diseases lead to blindness due to loss of photoreceptors, while neurons in the inner retinal layers are still preserved. We developed a system substituting the lost photoreceptors with photovoltaic arrays. Visual information captured by a camera is projected onto the subretinal implant from augmented-reality glasses using pulsed near-infrared (880nm) light. Photovoltaic pixels convert this light into electric current, stimulating the second-order retinal neurons, which then pass visual information through the retinal neural network to the brain. This approach preserves many features of natural vision, simplifies surgery by avoiding bulky electronics and wiring, allows scaling the number of electrodes to thousands and retains normal association of eye movements with visual perception.
Photovoltaic arrays implanted in patients blinded by age-related macular degeneration provides monochromatic form vision perceived simultaneously with the remaining peripheral natural vision. Clinical trials with 43 patients across 17 centers in 5 European countries demonstrated letter acuity matching their 100mm pixel size (20/420). Electronic zoom enables patients to read and write smaller fonts, improving visual acuity, on average, by 5 lines of the vision chart – up to 20/63.
Decreasing the pixel size for higher resolution is challenging due to reduced penetration depth of electric field in tissue. We developed various strategies for shaping the electric field, including current steering and 3-dimensional electrodes. With this new design, grating acuity with 40mm pixels in rats matched the pixel pitch, while with 20mm, it reached their natural resolution limit of 28mm. If successful in clinical trials, implants with 20mm pixels have the potential to increase acuity up to 20/80 without zoom, providing highly functional restoration of sight to millions of patients blinded by retinal degeneration.
About the speaker: Daniel Palanker is a Professor of Ophthalmology and by courtesy, of Electrical Engineering at Stanford University. He received PhD in Applied Physics (biomedical optics) in 1994 from the Hebrew University of Jerusalem, Israel, and postdoctoral training in Physics (ultrafast lasers) in 1996-1998 at Stanford University, CA.
Dr. Palanker studies interactions of electric field with biological cells and tissues, and develops optical and electronic technologies for diagnostic, therapeutic, surgical and prosthetic applications, primarily in ophthalmology. In the field of laser-tissue interactions, his group developed several ophthalmic laser systems, including Pattern Scanning Laser Photocoagulator (PASCAL, Iridex) and Femtosecond Laser for Cataract Surgery (Catalys, J&J). In the field of electrosurgery, he developed the scalpel-size electrosurgical tool with single-cell precision (PlasmaBlade, Medtronic). In the area of ophthalmic imaging, he is working on optoretinography – label-free imaging of neural signals based on phase-resolved OCT.
In the field of electro-neural interfaces, his lab developed the photovoltaic subretinal prosthesis for restoration of central vision in patients blinded by retinal degeneration (PRIMA), neural stimulator for enhancement of tear secretion (TrueTear, Allergan) and devices for electronic control of blood flow.
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