Retinal degenerative diseases lead to blindness due to loss of the image capturing photoreceptor layer, while neurons in the image processing inner retinal layers are preserved to a large extent. Electronic retinal prostheses seek to restor sight by electrical pattern stimulation of surviving neurons. Very encouraging clinical results with the first retinal prostheses have been recently demonstrated. However, current implants are powered through inductive coils, requiring complex surgical methods to implant the coil-decoder-cable-array systems, which deliver energy to stimulating electrodes via intraocular cables. We developed a photovoltaic subretinal prosthesis, in which silicon photodiodes in each pixel directly convert pulsed near-infrared (NIR) images projected from video goggles into local electric currents to stimulate neurons. This system offers multiple advantages over other designs: due to wireless activation of the pixels in the implant the system is scalable to thousands of electrodes; it maintains the natural link between eye movements and image perception; the implantation is greatly simplified and modular design of the implant allows expanding the visual field by tiling; pillar electrodes allow cellular-scale proximity to the targe neurons. Such a versatile system could be used to address the divergent needs of patients with various forms of retinal degeneration. We have manufactured and tested the first generation of the implants. Photovoltaic arrays show long-term biocompatibility, and provide safe retinal stimulation upon illumination with NIR pulses in-vitro and in-vivo. We now seek to produce the implants designed for highest resolution and lowest stimulation thresholds, and protected by inert and biocompatible coatings for long-term implantations. To achieve these goals we will assess visual acuity and contrast sensitivity obtained with subretinal photovoltaic implants of different designs in-vitro and in-vivo in animals with normal and degenerate retinas. This project brings together a unique combination of engineers, neuroscientists and ophthalmologists to complete the development and evaluation of a high-resolution retinal prosthetic system designed specifically for achieving the functional levels of vision.
Retinal degenerative diseases lead to blindness due to loss of the 'image capturing' photoreceptor layer, while neurons in the 'image processing' inner retinal layers are preserved to a large extent. We developed a photovoltaic subretinal prosthesis, in which photodiodes in each pixel directly convert pulsed near- infrared images projected from video goggles into local electric currents and stimulate neurons. This system is scalable to thousands of pixels, is easily implantable, and maintains the natural link between eye movements and image perception. This innovative design has the potential to addresses the divergent needs of patients with various forms of retinal degeneration.
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