A Smart Contact Lens for Eye Injuries

A smart contact lens fitted with an artificial iris could help people with eye injuries and congenital diseases see better. The lens, described this week at the International Electron Devices Meeting in San Francisco, uses concentric LCDs to mimic the expansion and contraction of the pupil that’s normally controlled by the iris.

The artificial iris is part of a larger project on smart contact lenses led by Herbert De Smet, a professor who works on intelligent sensors at the University of Ghent. De Smet’s group is working on putting many electronic components onto these lenses, including batteries, antennas, control electronics, and chemical sensors.

The lens presented at the San Francisco meeting is aimed at helping about 200,000 people who suffer from problems with the iris, whether due to cancer, an acute injury, or genetics. The iris is the colored part of the eye surrounding the pupil. It contracts under bright light to protect the retina from, say, the rays of the full sun, and expands in low light to help us see better. When the iris is absent or damaged and therefore can’t contract, being out in the sun or just under bright indoor light is painful.

The usual solution is to wear dark sunglasses or a dark contact lens, says Florian De Roose, a researcher at Imec in Leuven, Belgium. But it’s difficult to see in low light when wearing sunglasses. And people with damaged irises may find that daylight is still too bright despite wearing tinted lenses. A contact lens that darkens to block out light and effectively constricts the pupil could help people to see better.

De Smet is collaborating with De Roose and other researchers to make parts for the artificial iris system. De Smet’s group has already integrated liquid crystal cells onto contact lenses; De Roose worked on adding flexible control electronics. On the lens, three concentric LCDs surround a clear central area that sits above the pupil. In bright light, all three LCDs can be activated, causing the artificial iris to contract and narrow the opening. In dim light conditions, all the LCDs are turned off, and the artificial iris expands to let more light in. Around the iris are ten organic solar cells and control electronics containing a driver for each of the three LCD rings.

De Roose’s Imec group worked on flexible, low-power driver electronics that take up about 0.75 square millimeters. They used thin-film transistors, based on transparent IGZO, built on a flexible polymer. The control chip is placed at the edge of the lens so that it doesn’t occlude vision. However, the completed chip has a transparency of about 50 percent, so it could be made larger. The system draws 25 microwatts—which the onboard photovoltaics should be able to supply.

So far, all the parts have yet to be integrated. The collaborators have shown that they can build LCDs, solar cells, and drivers on the lens and that the driver can control the LCD; now they have to show that the full system can operate together with the solar cells. In future systems, says De Roose, the photovoltaics will act both as the light-level sensors and the LCD power source. “The beauty of this is, the more light there is available, the more power there will be to drive the LCDs” and to make the iris contract, says De Roose. He also notes that while the group hasn’t focused on aesthetics, organic photovoltaics can be made in colors that could look relatively natural.

The smart contact lens project faces broader challenges. Such lenses must do more than carry workable sensors and display elements. They must also be carefully mechanically engineered. The lenses themselves are stretchy, but the transistors are merely flexible. The researchers will have to account for this mismatch, either by moving to stretchy materials or being very careful about the smart lens architecture. And more importantly, they must ensure that these lenses are safe. One way they’ll do that is by ensuring that the electronic components don’t interfere with the transfer of water and oxygen through the lens to the cornea. Otherwise, the lens could cause infections.

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