Geneva: Researchers have unveiled the latest version of a first of its kind telescopic contact lens that allows the wearer to zoom in and out with the wink of an eye.
The contact lenses have to be paired with smart glasses that recognise winks and ignore blinks to allow wearers to switch between normal and magnified vision.
"We think these lenses hold a lot of promise for low vision and age-related macular degeneration (AMD)," said Optics specialist Eric Tremblay from Ecole Polytechnique Federale de Lausanne in Switzerland.
There are glasses already on the market for people with AMD that have mounted telescopes, but they tend to look bulky and interfere with social interaction.
They also do not track eye movement, so users have to position their eyes and tilttheir head to use them. The first version of the telescopic contact lens - which magnifies 2.8 times - was announced in 2013.
Since then scientists have been fine-tuning the lens membranes and developing accessories to make the eyewear smarter and more comfortable for longer periods of time, and thus more usable in every day life.
The lenses work by incorporating a very thin reflective telescope inside a 1.55mm thick lens.
Small mirrors within bounce light around, expanding the perceived size of objects and magnifying the view, so it's like looking through low magnification binoculars.
At this time, the telescopic contacts are made using a rigid lens known as a scleral lens - larger in diameter than the typical soft contacts you might be used to and valuable for special cases, such as for people with irregularly shaped corneas, researchers said.
Although large and rigid, scleral lenses are safe and comfortable for special applications, and present an attractive platform for technologies such as optics, sensors, and electronics like the ones in the telescopic contact lens, researchers said.
The final lenses are made from several precision cut and carefully assembled pieces of plastics, aluminum mirrors, and polarising thin films, along with biologically safe glues.
Since the eye needs a steady supply of oxygen, the researchers have spent the last couple of years making the lenses more breathable - a critical requirement.
To achieve oxygen permeability, they are incorporating tiny air channels roughly 0.1mm wide within the lens to allow oxygen to flow around and underneath the complex and normally impermeable optical structures to get to the cornea.
The electronic glasses paired with lenses use a small light source and light detector to recognise winks and ignore blinks. The wearer will wink their right eye for magnification, and left eye for normal vision.
This switching functionality is crucial for the lenses to be widely useful for non-AMD sufferers who will be able to have magnification "on demand."
The lens prototype was unveiled at a meeting of the American Association for the Advancement of Science (AAAS) in San Jose, California.