Photovoltaic Retinal Implants Are Powered By The Images They See

Powering Retinal Implants
Using near-infrared light, researchers have found a way to deliver video images and electrical power to retinal implants with the same signal.

The idea of restoring sight to people with damaged or degenerating photoreceptors in their eyes is simple enough in concept -- place a photoreceptor implant in the eye and beam video from a camera to the implant, bypassing the faulty photoreceptors. However, powering a device implanted in the back of a person's eye indefinitely is a serious obstacle. But Stanford researchers have worked around the problem by beaming images to the implant by pulsing near-infrared light that delivers both data and power to the implanted chip.

The 3-millimeter-wide implant is designed like an array of miniature solar cells configured in three layers that are 30 micrometers thick altogether. The array is essentially a collection of pixels, each connected to the next by 300-nanometer-thick silicon joints that allow the array to curve along the natural shape of the retina. To put it another way, the implant is flexible and extremely small.

A visually impaired person with the implant wears a set of exterior glasses that hosts a video camera that delivers a feed to the implant. A pocket PC then translates the video into 900-nanometer-wavelength light that delivers both the image data and electricity to the implant. The researchers chose an invisible, near-infrared display for the goggles because some people suffering from degenerating photoreceptors might still have some perception left, which would register visible light and interfere with the image being projected.

The quality of vision that the rig provides is limited, but the fact that researchers have found an innovative way to deliver both power and images in the same package is a relative breakthrough, as it should inform other efforts at sight restoration on a means to sustainably power remote implants deep in the eye.