A video camera transmits images to a processor, which displays the images on an LCD screen on the inside of patient’s goggles. The LCD display transmits infrared light pulses that project the image to photovoltaic cells implanted underneath the retina. The photovoltaic cells then convert light signals into electrical impulses that in turn stimulate retinal neurons above them.
A flexible retinal implant, combined with sophisticated electronics, may provide a higher degree of vision to blind patients with retinal degeneration. The resolution is higher, and improved software highlights the edges of objects, making them more recognizable.
The Stanford implant has approximately 1,000 electrodes, compared to 60 electrodes commonly found in fully implantable systems.
What’s more, patients would not have to move their heads to see, as they do with older implants. Although we don’t notice it, images fade when we do not move our eyes, and we make several tiny eye movements each second to prevent fading. With older retinal implants, the camera moves when the head moves, but not when the eyes move.
The Stanford implant, on the other hand, retains the natural link between eye movements and vision, Palanker said. A patient would wear a video camera that transmits images to a processor, which displays the images on an LCD screen on the inside of patient’s goggles. The LCD display transmits infrared light pulses that project the image to photovoltaic cells implanted underneath the retina. The photovoltaic cells convert light signals into electrical impulses that in turn stimulate retinal neurons above them.
This is also the first flexible implant, and it makes use of a material commonly used in computer chips and solar cells. Peumans and his team at the Stanford Nanofabrication Facility engineered a silicon implant with tiny bridges that allow it to fold over the shape of the eye. “The advantage of having it flexible is that relatively large implants can be placed under the retina without being deformed, and the whole image would stay in focus,” Palanker said. A set of flexible implants can cover an even larger portion of the retina, allowing patients to see the entire visual field presented on the display.
The Stanford device is implanted under the retina, at the earliest possible stage in the visual pathway. “In many degenerative diseases where the photoreceptors are lost, you lose the first and second cells in the pathway,” Baccus said. “Ideally you want to talk to the next cell that’s still there.” The goal is to preserve the complex circuitry of the retina so that images appear more natural.