People with age-related macular degeneration (AMD) experience progressive vision loss in parts of their retinas. Typically, either specialty glasses or surgically implanted telescopic lenses are used to project images to the healthy parts of the retina. The glasses are uncomfortable and look goofy, resembling ones surgeons use with telescopes protruding from the front.
Now a team of researchers from U.S. and Switzerland, funded by DARPA, are reporting the development of a contact lens, that works in conjunction with active polarized glasses, to provide both normal and telescopic projection of light onto the retina. The contact lens has two built-in lenses, one in the center that simply adjusts where the light is projected and one around it that has a zoom of 2.8 magnification. Both send light to the same region of the eye, but because they’re polarized perpendicular to each other, basically the same glasses that are used for viewing movies on 3D TV’s can be adapted to allow the wearer to change through which lens light gets to the eye.
From the Optical Society:
The team tested their design both with computer modeling 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. In constructing the lens, researchers relied on a robust material commonly used in early contact lenses called polymethyl methacrylate (PMMA). The team needed that robustness because they had to place tiny grooves in the lens to correct for aberrant color caused by the lens’ shape, which is designed to conform to the human eye.
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 by consumers. The researchers report that the grooves used to correct color 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. Finally, the robust material they used, PMMA, is not ideal for contact lenses because it is gas-impermeable and limits wear to short periods of time.
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 color without the need for grooves to bend the light.
Study in Optics Express: Switchable telescopic contact lens