Butterfly's Wings That Could Save People's Vision
Science & Tech / /
To stay hidden from predators, patterns on the wings of a South American butterfly go completely transparent. This was used by the engineers who have mimicked these patterns in an eye implant for people with glaucoma.
Glaucoma is an eye disease that affects the optic nerve, in some cases causing even irreversible blindness. Although eye pressure is measured when people come in for checkups, it can fluctuate dramatically, and not only between visits, but also over the course of a day.
“There’s times when the pressure really spikes,” says Hyuck Choo, a medical and electrical engineer at the California Institute of Technology in Pasadena and co-author of a study. “It seems that’s when the damage is being done to the optic nerve.”
Pressure in the eyes can be reduced by taking certain medications, knowing exactly the right timing of taking them could give people a better shot at saving their vision. “They must be able to monitor this pressure round the clock, 24 hours a day,” Choo says.
A team of experts are working on designing an eye implant the size of a sesame seed that would reveal changes in pressure when a light shines on them. As Popular Science reports, the implant is built from a flexible membrane stretched over a mirror with a small empty space in between. When pressure inside the eye increases, the membrane bends. This makes the gap narrower, changing the wavelength of reflected light. It is expected that people with this implant would be able to use the light from a cell phone to track their eye pressure even at their own homes.
Currently, the implant is able to give accurate values of the eye pressure if the light and pressure-reading device were positioned in front of the eye. But the aim is to also make it accessible for people with shaky hands, Choo says. “The patient must be able to make measurements easily, instead of going through this tedious optical alignment procedure.”
The glasswing butterfly’s wings were an inspiration which seems to offer a way around this problem. This insect with transparent wings has dome-shaped structures arranged in patterns allowing the light to pass through the wings, instead of reflecting back. But it also uses another, unique trick to make its wings transparent. The part of the wing close to its body has nanostructures that are arranged farther apart. This helps scattering visible light in all directions.
Choo and his team used this knowledge to make implants with similar patterns and tested them in rabbits. Results showed that these implants were about 3 times more accurate compared with those with flat membranes. Other benefit is the nanopillars’ redirection property, known as angle-independent antireflection. This could be used to ensure that light would always pass through the eye implant, making the device angle-insensitive and providing an accurate reading regardless of where the reader is held.
The implant would hopefully be tested on people in 3 years. Except for warning of dangerous spikes in pressure, the implant could collect information about how a patient’s eye pressure varies over time so that a tailored treatment would be make more effectively.