Modern sight correction medical procedures often involve surgery where an artificial lens is implanted. The patient’s sight is significantly improved, however the quality of vision is far from that experienced with a healthy pair of eyes. That’s because current artificial lenses function more or less like those from a camera, a bit more advanced of course. The eye is a lot more complicated, on the other hand. Recently a team of researchers have successfully constructed a lens that is closer to the human eye than any of its counterparts.
During high school optics, textbooks and teachers would often use the human eye as an allegory for a natural light bending lens. Then they would compare it to a camera, when discussing refraction – the bending of light in a particular direction when traveling through a new medium. Fact of the matter is, a camera’s lens is only comprised of only one or a few other layers. As light passes through the lens, it’s bent only at the surface of the lens, and then exits in a straight line. This is why artificial lens implants, while still improving sight considerably, aren’t that effective.
The eye, however, bends light continuously. To create an artificial lens with features closer to the natural qualities of the eye, scientists at Case Western University, the Rose-Hulman Institute of Technology, the U.S. Naval Research Laboratory, and Case Western spin-off company PolymerPlus made a single lens from hundreds of thousands of layered and laminated nanoscale polymer films. The technology is known as GRIN (gradient refractive index optics).
Each of these thousands of stacked films has slight different optical properties, which causes light to be incrementally bent by multiple degrees as it passes through the lens.
“As light passes from the front of the human eye lens to the back, light rays are refracted by varying degrees,” said Michael Ponting, president of PolymerPlus. “It’s a very efficient means of controlling the pathway of light without relying on complicated optics, and one that we attempted to mimic.”
Lenses currently employed by today’s technology and used to treat sight impairment conditions, like cataract, lack the ability to incrementally change the refraction of light, and thus fail to come close to the performances of the human eye.
“A copy of the human eye lens is a first step toward demonstrating the capabilities, eventual biocompatible and possibly deformable material systems necessary to improve the current technology used in optical implants,” says Ponting.
Since the technology also enables optical systems with fewer components, GRIN could be used not only as medical implants, but also in consumer and military products.
“Prototype and small batch fabrication facilities exist, and we’re working toward selecting early adoption applications for nanolayered GRIN technology in commercial devices,” says Ponting.
Findings were published in the journal Optics Express.The animation below describes the M-GRIN manufacturing process used to make the new lenses: