Contact lenses are wonderful for correcting vision in most people, but do little for those suffering from age-related macular degeneration (AMD), who often lose the ability to see small details like the contours of a face or letters on a page. To tackle AMD's special version of blurriness, an international team has designed contact lenses with a built-in zoom that could one day be used by people with AMD.
Rather than being out of focus, eyes with AMD lose the center of their visual field due to damage to the retina. However, peripheral areas of the retina, along with peripheral vision, remain in tact.
If light entering the eye could be redirected onto these healthy areas, it might restore regular sight. At least this was the idea put forth in this study by Dr. Joseph Ford, an electrical and computer engineer at the University of California, San Diego.
He and a team of Swiss collaborators designed a contact lens that takes light as it hits the eye and magnifies it onto peripheral parts of the retina. They tested the lens on a life-sized model of a human eye and found that it could magnify the view by three times.
The zoom-in function for the contact lenses is always active, so in order to switch it on and off, a person would need to wear a special set of 3-D TV glasses made by Samsung. When turned on, liquid crystals in the glasses rearrange to block light to the magnifying portions of the contact lenses.
Images captured through the contact lens and mechanical model eye are shown. c) Outdoor image taken with model eye alone. d) Outdoor image taken with model eye and contact lens. This image shows why each of the two magnification states (normal and 2.8x) should be used one at a time: Here, neither section of the lens is being blocked by the glasses, and the result is an image with greatly reduced contrast. e) Outdoor image taken with just the magnified outer portion of the contact lens (2.8x). (Credit: Optics Express)
As the leading cause of legal blindness in Americans over 55, solutions for AMD are in high demand.
Ford's contact lens and 3-D glasses system, which was funded by DARPA, would be a significant improvement to the current optical magnifier eyeglasses, which are bulky and not very sleek.
"For a visual aid to be accepted it needs to be highly convenient and unobtrusive," said co-author and engineer 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."
The plastic infused into this prototype lens can't be used with human eyes, but the authors are confident that they can find a safe alternative.
"In the future, it will hopefully be possible to go after the core of the problem with effective treatments or retinal prosthetics," said Tremblay. "The ideal is really for magnifiers to become unnecessary. Until we get there, however, contact lenses may provide a way to make AMD a little less debilitating."
Front view of the switchable telescopic contact lens. Credit: Optics Express.
Source: Tremblay EJ, Stamenov I, Beer RD, Arianpour A, Ford JE. Switchable telescopic contact lens. Optics Express. 2013.