Researchers have designed the world's first 'Terminator-style' contact lens that would allow wearers to zoom in and zoom out.
The 1.17 mm-thick prototype contains two separate optical paths: one for magnified vision and one for regular vision.
Wearers will be able see normally through the central region, while selective blocking makes it possible for the user to switch between the two types of view.
Thus, the user can effectively zoom in and out.
Researchers from the US and Switzerland led by University of California San Diego Professor Joseph Ford said, with refinements, the system could offer Age-Related Macular Degeneration (AMD) patients a relatively unobtrusive way to enhance their vision.
"For a visual aid to be accepted it needs to be highly convenient and unobtrusive," said co-author Eric Tremblay of the Ecole Polytechnique Federale de Lausanne (EPFL).
The new lens system uses tightly fitting mirror surfaces to make a telescope that has been integrated into a contact lens just over a millimetre thick.
The lens has a dual modality: the center of the lens provides unmagnified vision, while the ring-shaped telescope located at the periphery of the regular contact lens magnifies the view 2.8 times.
To switch back and forth between the magnified view and normal vision, users would wear a pair of liquid crystal glasses originally made for viewing 3-D televisions.
These glasses selectively block either the magnifying portion of the contact lens or its unmagnified center.
The liquid crystals in the glasses electrically change the orientation of polarised light, allowing light with one orientation or the other to pass through the glasses to the contact lens.
The team tested their design both with computer modelling and by fabricating the lens. They also created a life-sized model eye that they used to capture images through their contact lens-eyeglasses system.
Researchers used a robust material commonly used in early contact lenses called polymethyl methacrylate (PMMA).
Tests showed that the magnified image quality through the contact lens was clear and provided a much larger field of view than other magnification approaches, but refinements are necessary before this proof-of-concept system could be used.
The researchers report that the grooves used to correct colour had the side effect of degrading image quality and contrast. These grooves also made the lens unwearable unless it is surrounded by a smooth, soft "skirt," something commonly used with rigid contact lenses today.
The team is currently pursuing a similar design that will still be switchable from normal to telescopic vision, but that will use gas-permeable materials and will correct aberrant colour without the need for grooves to bend the light.
The study was published in the journal Optics Express.