Variable Focus Eyeglasses
Tired of the limitations of bifocals, progressive lenses and other multifocal eyeglass lenses for the correction of presbyopia? Newly developed variable focus lenses may be just the solution you're looking for.
The primary drawbacks of bifocals and other multifocal lenses are:
- Because they must have different lens powers for distance and near vision, the portion of the lens with the power you need for any given visual task is limited in size.
- The near vision portion of the lens frequently gets in the way when you want to see things in the distance such as when you want to look down at your feet when descending stairs or stepping off a curb.
To avoid these issues, some people with presbyopia choose to purchase several pairs of eyeglasses with single vision lenses one pair for distance vision, one pair for reading and another pair for computer work and other activities at arm's length. But this is expensive and cumbersome.
Recognizing these limitiations of conventional multifocal lenses, and the expense of multiple eyeglasses with single vision lenses, at least two eyewear manufacturers have come up with an innovative solution: variable focus eyeglass lenses.
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EmPower Variable Focus Eyeglasses
In March 2011, PixelOptics (Roanoke, Va.) formally introduced its emPower variable focus eyeglasses. The eyewear features lightweight composite lenses with a thin, transparent liquid crystal layer that electronically changes the power of the lenses to add magnifying power to a portion of the lens for reading when you need it, and make it disappear when you don't.
The microchip and power source for the adjustable focus lenses are hidden within the temples of the eyeglass frames, and the power change in the lens is silent and instantaneous. The glasses are waterproof and shock-resistant, and one overnight charge of the eyewear allows for 48 to 72 hours of operation, according to the company.
Wearers have the option of operating the emPower variable focus eyeglasses in three modes: manual on, manual off and automatic:
EmPower electronic variable focus eyeglasses, shown here on charging dock.
- When "manual on" is set, you can add or remove the near magnifying power of the lenses by making a quick swiping motion with you finger against the temple of the frame. With a second swipe, the magnifying power disappears, enabling a larger field of view for distance and intermediate viewing ranges.
- When "manual off" is set, the near power disappears, so there is no unwanted magnification getting in the way of distance and intermediate viewing. This setting is ideal for driving, for watching television and for sports activities such as golf or bicycling.
- When "automatic" is set, the near power zone in the lenses appears automatically when you lower your head slightly to read, and disappears when your head returns to an upright position. This setting is ideal for situations such as taking notes in a classroom or public speaking.
PixelOptics says its electronic emPower adjustable focus eyeglasses will be available in the southeastern region of the United States beginning in May 2011 and will be available nationwide by the end of the year. The company also plans to introduce the emPower eyeglasses in Europe in the second half of 2011 and in Asia in 2012.
The eyewear is designed to have the same weight, feel and look of high-fashion eyewear, according to the company, and frames will be available in 12 styles with multiple color options.
PixelOptics' emPower electronic adjustable focus glasses also will include lightweight high-index lenses and will be sold with a recharging dock.
Superfocus Adjustable Focus Eyeglasses
Superfocus adjustable focus eyeglasses have been commercially available since 2009, previously marketed under the name TruFocals.
Each "lens" in Superfocus eyeglasses is really a set of two lenses. The front lens of the set contains your distance vision prescription. The back lens (nearer the eye) has a rigid surface and a flexible one, and the space between them is filled with a clear optical fluid.
Superfocus adjustable focus eyeglasses (see diagram).
By moving a slider on the top of the frame's bridge, you push the fluid within the flexible lens forward, which alters the shape of the lens to add magnifying power for reading and other near or intermediate visual tasks.
Superfocus adjustable focus glasses offer the advantage of the entire surface area of the lens changing power, to provide the largest field of view possible for whatever task you adjust them for. However, the lenses do not have an automatic mode: you must manually adjust the slider on the frame's bridge to change the power of the lenses.
Superfocus eyeglasses have won several technology awards, including Popular Science's 2009 Best of What's New Award and The Wall Street Journal's 2010 Innovations Silver Award. The glasses are manufactured in the United States by Superfocus LLC (Van Nuys, Calif.).
In February 2011, Superfocus LLC announced the National Aeronautics and Space Administration (NASA) certified its variable focus eyeglasses for use by astronauts on the Discovery space shuttle and aboard the International Space Station. Since the average age of U.S. astronauts today is 48, Superfocus glasses will help many of them perform tasks that presbyopia can make difficult, such as viewing overhead instrument panels, said C. Robert Gibson, OD, a vision consultant to NASA Space Medicine.
Self-Adjustable Glasses for the Developing World
A different type of variable focus eyeglasses is self-adjustable glasses. These glasses are targeted for use in developing countries to reduce visual disability caused by uncorrected refractive errors in areas where residents do not have access to eye doctors, eye exams and prescription eyeglasses.
Self-adjusting eyeglasses are not designed to be true variable focus eyeglasses like emPower or Superfocus eyeglasses, but the power of the lenses can be adjusted as needed if the wearer's refractive error changes or the glasses are later used by someone else.
Though the vision correction obtained with self-adjustable eyeglasses typically is not as accurate as what would be prescribed by an eye care professional, a recent study found that more than 90 percent of Chinese schoolchildren ages 12 to 17 were able to obtain visual acuity of 20/25 or better with the glasses.*
Adspecs are self-adjustable glasses developed in the U.K. by Dr. Josh Silver, professor of physics at the University of Oxford. The eyewear features flexible lenses that are filled with a clear fluid. You put the glasses on and, using a syringe-like device, add or subtract fluid to alter the shape of the lenses until your vision is optimized. Once this lens shape is achieved, the lenses are sealed, to maintain focus.
Adspecs self-adjustable eyeglasses (see closeups). (Image: Centre for Vision in the Developing World)
Adspecs are distributed through Dr. Silver's Oxford-based humanitarian organization, the Centre for Vision in the Developing World. Currently, the self-adjustable single vision lenses can correct nearsightedness, farsightedness (and presbyopia), but not astigmatism.
In March 2011, the Centre announced its new Child ViSion initiative, which is being sponsored by Dow Corning Corporation. The project will design, manufacture and distribute 50,000 pairs of self-adjustable glasses to teenagers aged 12-18 in the developing world, primarily through and in support of education programs.
The Centre and Dow Corning also will work together to create a new design of Adspecs self-adjustable glasses that are lighter, better-looking and more suited to children ages 12 to 18.
Eyejusters are another type of self-adjusting eyeglasses being developed in the U.K. for use in the developing world. The glasses are being created by Oxford-based Eyejusters Ltd, a private company. (Eyejusters Ltd is not affiliated with the Centre for Vision in the Developing World, but several members of the company's management team are friends of Dr. Silver and have been involved with the Centre's Adspecs project.)
Eyejusters self-adjustable eyewear (see closeup).
Instead of fluid-filled lenses, each "lens" of the Eyejusters eyewear is a set of lenses. The power of each lens set is adjusted by how the individual lenses are positioned in relation to each other, which is controlled by a removable magnetic turn-screw in the temple of the Eyejusters frame.
Like Adspecs, Eyejusters self-adjusting glasses can correct nearsightedness and farsightedness, but not astigmatism.
According to the company, Eyejusters self-adjustable eyeglasses have thinner lenses than the original Adspecs eyeglasses and will feature an attractive metal frame that will be available in several colors. Eyejusters are expected to be available in mid-2011.
About the Author: Gary Heiting, OD, is senior editor of AllAboutVision.com. Dr. Heiting has more than 25 years of experience as an eye care provider, health educator and consultant to the eyewear industry. His special interests include contact lenses, nutrition and preventive vision care. Connect with Dr. Heiting via Google+.
[Page updated June 2011]
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