Contact lenses are not useful in improving blurry vision of those suffering from age-related macular degeneration (AMD), the leading cause of blindness among older adults in the western world.
That's because simply correcting the eye's focus cannot restore the central vision lost from a retina damaged by AMD. Now a team of researchers from the United States and Switzerland led by University of California San Diego Professor Joseph Ford has created a slim, telescopic contact lens that can switch between normal and magnified vision. With refinements, the system could offer AMD patients a relatively unobtrusive way to enhance their vision. The team reports its work today in the Optical Society's (OSA) open-access journal Optics Express
Visual aids that magnify incoming light help AMD patients see by spreading light around to undamaged parts of the retina. These optical magnifiers can assist patients with a variety of important everyday tasks such as reading, identification of faces, and self-care. But these aids have not gained widespread acceptance because they either use bulky spectacle-mounted telescopes that interfere with social interactions, or micro-telescopes that require surgery to implant into the patient's eye.
"For a visual aid to be accepted it needs to be highly convenient and unobtrusive," says co-author Eric Tremblay of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. A contact lens is an "attractive compromise" between the head-mounted telescopes and surgically implanted micro-telescopes, Tremblay says.
The new lens system developed by Ford's team uses tightly fitting mirror surfaces to make a telescope that has been integrated into a contact lens just over a millimeter 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switch back and forth between the magnified view and normal vision, users would wear a pair of liquid crystal glasses originally made for viewing 3-D televisions.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 polarized light, allowing light with one orientation or the other to pass through the glasses to the contact lens.