A telescopic contact lens capable of magnifying the image of the surrounding world could give sight back to those affected by age-related vision degeneration.
Developed as part of a project funded by the US defence agency Darpa, the telescopic contact lens consists of two separate layers – one for seeing the world as it is, the other allowing the wearer to zoom in up to three times.
To switch between the two vision modes is simple – just blinking with one eye while wearing special glasses.
"We think these lenses hold a lot of promise for low vision and age-related macular degeneration (AMD),” said Eric Tremblay, from the Federal Polytechnic School of Lausanne in Switzerland, who led the Darpa-funded research.
"A lot of people with severe AMD are really desperate for things they can try. The lenses would mostly be used for distance work, maybe when driving, and also for recognising faces."
The prototypes developed jointly by the Lausanne team and Darpa have been tested by five volunteers.
"Darpa fund things that are really out there - forward-thinking stuff,” Tremblay said.
"They're really interested in super-vision. They'd like to produce a pair of binoculars you can put on in the blink of an eye, which is really cool but it's further than where we are today."
The lens system works by using polarised light to switch from normal to magnified vision.
Sensors on the glasses respond to reflected light bouncing off the contact lenses by allowing only those rays polarised in a certain direction to reach the contact lenses. Each lens component is sensitive to a different twist of polarised light.
The volunteers reported that they could see with the lenses and glasses, but their vision was a little blurred.
Tremblay said it might be two more years before the system is good enough to be used to help patients with AMD.
"People with AMD use their peripheral vision to see to the side of their blind spot," he added. "When they try to read it's difficult because your visual acuity really falls off away from the centre."
The next stage in the project is finding a way to make the lenses more "breathable" so they are less irritating to wear.