Things are really looking up for people who suffer from vision loss.
Scientists from Sweden and Israel teamed up to develop the thinnest retinal implant in the world. The wireless device is layered with gold and organic tattoo ink. The replacement retina contains no silicone and is a remarkable 500 times less thick than any other retinal implant on the market today.
This is great news for the 39 million blind people alive today plus the additional 245 million people with moderate to extreme vision impairments.
Malfunctioning photoreceptors – the layer of rods and cones inside the eyeball – are at the root of most cases of blindness and vision loss:
“The retina is a thin membrane on the back of the eye that converts incoming light into electrical signals that are then processed by the brain. The retina is only half a millimeter thick but contains three distinct cellular layers. The bottom layer, farthest from the light source, holds the rods and cones, also known as photoreceptor cells. It’s the photoreceptor layer that’s compromised in people with retinal diseases.”
In macular degeneration and retinitis pigmentosa, the slow atrophy and ultimate failure of the body’s natural rods and cones in the retina causes vision loss.
Glial cells in the top layer of the retina receive electrical impulses from the photoreceptors and transmit them through the optic nerve for image processing by the brain. In the 1980s, researchers found a way to bypass the rods and cones completely and route electrical signals directly to the glial cells.
The most sophisticated “bionic eye” available today is the Argus II Retinal Prosthesis System developed by California-based Second Sight. An external video camera mounted on a pair of sunglasses captures images for transmission to a small video-processing unit the patient carries. The images are converted into electrical impulses that are sent wirelessly to an array of electrodes implanted in the back of the eye. The implant broadcasts the electrical signals to the glial cells which relay them to the brain for interpretive processing.
Bionic eyes have several definite shortcomings: they can only be implanted in one eye, patients must wear a power source and processor at all times, and the most successful cases improve visual acuity only to the low level of 20/1200 – normal vision is considered 20/20 – with no ability to recognize color and limited perception.
Two Chinese researchers, Jiayi Zhang and Gengfeng Zheng at Fudan University in Shanghai, invented a new way to bypass the eye’s photoreceptor layer and make a direct connection to the glial cells by means of semiconducting nanowires of titania flecked with gold nanoparticles that model the form and function of natural, healthy photoreceptors.
The team built the device by painting two layers of organic pigment on a base layer of gold. They immersed this superconductor “sandwich” in a saltwater solution similar to the environment inside an eyeball. When exposed to light, the device charges and generates an electric field that stimulates nearby vision neurons.
The Chinese research duo claims that their prosthetic retina does restore full-color vision and needs no external power or processor devices to operate. Because it is made from organic material, the risk of rejection associated with silicone-based implants may be much lower with the new artificial retina.
Zhang and Zheng tested their prosthetic system in cultured neurons and in retinas from chicken embryos before they had developed photoreceptors. The device created enough electricity in both scenarios to power surrounding retinal neurons.
Live rabbits are being used as test subjects now to see if the retinal implant can transmit a response to red light, which rabbits are unable to detect normally.
One final encouraging innovation in the medical field of artificial retinas comes from a New Jersey company called Natcore which is developing a retinal implant that is powered by the sun.
The solar-powered implant doesn’t need a camera, a transmitter, or any other external device in order to function. It can work if the patient’s nerves are alive and only the rods and cones are damaged. The design calls for wavelength selection which could restore the ability to see colors.
This prosthetic consists of a flat round disc, about the size of a pencil eraser, that is surgically implanted. Coated carbon nanotubes act as solar cells. Light entering the eye is focused onto the artificial retina by the lens, causing a voltage buildup which triggers a visual signal transmission to the brain. In this remarkable device, the nanotubes not only generate solar power but they replace the body’s native photoreceptor cells.