Variable Focus Eyeglasses
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.
- No-line progressive lenses contain unavoidable aberrations in the lateral periphery of the lenses that can cause some wearers to experience noticeable blur and an undesirable feeling of movement or "swim," especially with quick head movements.
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 limitations of conventional multifocal lenses, and the expense of multiple eyeglasses with single vision lenses, eyewear manufacturers have come up with an innovative solution: variable focus eyeglass lenses.
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Adlens variable focus eyewear features an exclusive frame and lens combination with self-adjustable lenses that enable the wearer to focus on objects at any distance.
Each variable focus lens in Adlens glasses contains an elastic membrane within a chamber between two thin, lightweight polycarbonate lenses. When fluid is injected into this chamber by turning a removable knob on the side of the frame, the elastic membrane bows inward or outward within the chamber, which changes the power of the overall lens system.
Adlens Focuss glasses with Variable Power Optics (see closeup).
Adlens offers a second variable focus lens technology called Alvarez. In this lens system, two thin, wave-shaped polycarbonate "plates" can be slid across each other by means of a small knob on the frame. The position of the two plates relative to each other determines the power of the overall lens system.
Adlens also is working on a new adjustable eyeglass lens technology called Variable Power Optics, which will enable wearers with presbyopia to even more conveniently switch the power of their Adlens glasses to see objects at all distances, according to the company.
Adlens glasses can correct nearsightedness, farsightedness and presbyopia, but cannot correct astigmatism.
The company currently offers four lines of Adlens variable focus eyewear: Adlens Adjustables, The John Lennon Collection, Hemisphere and Emergensee. More than 100,000 people around the world are wearing Adlens variable focus eyewear, according to the company.
Adlens variable focus glasses are designed for use as a temporary or spare pair of glasses, and the power of the lenses can be customized instantly to correct from -6 diopters (D) of nearsightedness to +3 D of farsightedness with the simple turn of a dial. They also can be adjusted for special visual needs, including reading and computer use, or used to manage fluctuating vision for people with poorly controlled diabetes or after eye surgery.
In an interview conducted by First Vision Media Group in August 2013, Graeme MacKenzie, Director of Industry Affairs at Adlens, had this to say about the versatility of Adlens glasses:
"Given their utility the fact that you can just adjust the lens power they can be used in a really wide variety of situations. A lot of people use them at home in their home office environment because you can focus at different distances. A lot of people use them as a pair of monovision glasses, so one eye is set on the computer screen and the other is set on the keyboard. And that was quite a surprising find to us how easy it is for people to adapt to that and use the glasses in that way."
Adlens introduced Sundials in early 2014. The lightweight "spare pair" sunglasses offer UVA and UVB protection and have temple dials that adjust for near or far vision needs from -6D to +3D.
In October 2013, the company's Adlens Adjustables line received a Silver Stevie Award at the 10th annual International Business Awards in Barcelona, Spain. The product was recognized for its utility, craftsmanship and technology in the "Best New Product of the Year" category in Health and Pharmaceuticals.
Also in October 2013, Adlens introduced its new Focuss by Adlens variable focus progressive lenses and announced it had entered into a partnership with LensCrafters, a U.S. retail division of Luxottica, to test the product via an exclusive arrangement through the first half of 2014.
The new Focuss variable focus lenses incorporate distance and reading into one shared lens, and also correct astigmatism. Users turn a dial on the side of the frame to quickly adjust their prescription to the optimum power for distance, intermediate or near vision, depending on their needs at the time.
Adlens was founded in 2005 by James Chen, a Hong Kong-based businessman, and Dr. Joshua Silver, professor of atomic physics at Oxford University in the U.K. In addition to selling variable focus eyewear to consumers online and via select retailers, the company has established philanthropic programs to bring accessible vision correction to the developing world, particularly to areas where little or no affordable eye care is available.
Dr. Silver also is CEO of the Centre for Vision in the Developing World at St. Catherine's College in Oxford (see below).
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 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.
In February 2011, Superfocus LLC announced the National Aeronautics and Space Administration (NASA) had 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 can 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.
Empower variable focus eyewear was introduced by U.S.-based PixelOptics in 2011.
The eyeglasses featured lightweight composite lenses with a thin, transparent liquid crystal layer that electronically changed the power of the lenses to add magnifying power for reading and other near vision tasks when needed and quickly remove it when it wasn't needed.
The microchip and power source for the lenses were hidden within the temples of the frames, and wearers had the option of operating the electronic glasses in three modes: manual on, manual off and automatic:
Empower electronic variable focus eyeglasses, shown here on charging dock.
- When "manual on" was set, the wearer could change the power of the lenses by making a quick swiping motion with a finger against the temple of the frame. With a second swipe, the magnifying power disappeared, enabling a large, unobstructed field of view for distance vision.
- When "manual off" was set, the near power disappeared, so no unwanted magnification got in the way of distance and intermediate vision for driving, watching television, sports activities, etc.
- When "automatic" was set, added magnifying power appeared in the lower portion of the lens when the wearer lowered his or her head to read, and disappeared when the head returned to an upright position.
But in November 2013, PixelOptics announced it was going out of business and would file for Chapter 7 bankruptcy.
Under the terms of the bankruptcy, the court was to appoint an executor to oversee liquidation of the company's assets, including an intellectual property portfolio of more than 400 patents and patent applications, many of which involve electronic variable focus eyeglasses.
Adjustable Focus Glasses Humanitarian Efforts
In addition to the vision-related philanthropic work being done by Adlens in Rwanda and other African countries, two other organizations that are bringing variable focus and self-adjustable eyeglass lens technology to the developing world are the Centre for Vision in the Developing World and Eyejusters, both based in Oxford, U.K.
Centre for Vision in the Developing World. The stated mission of the Centre for Vision in the Developing World (CVDW) is "to help people in the developing world to see clearly, thus improving their quality of life and economic potential."
Adspecs self-adjustable eyeglasses (see closeups). (Image: Centre for Vision in the Developing World)
The primary interest of the organization is to enable a person with vision problems due to uncorrected refractive errors to correct his or her own vision without requiring an eye exam by a highly trained eye care professional.
"We believe that this approach can help the large and growing unserved population of over one billion people in a cost-effective and timely fashion," CVDW says on its website.
Adspecs were the first self-adjustable glasses developed by Dr. Silver and distributed by CVDW in the developing world.
To change the power of Adspec lenses, the user turns a wheel on a syringe on the side of the frame to pump more or less silicone oil into a chamber formed by two flexible lens membranes that are protected by a rigid outer lens made of plastic. After the lenses are adjusted for the best vision possible, the user simply tightens the screws on each side of the frame and removes the syringes.
More than 30,000 pairs of Adspecs glasses have been distributed in developing countries worldwide by various humanitarian programs, including the Humanitarian and Civic Assistance Program of the U.S. military, according to CVDW. Another 10,000 Adspecs glasses have been distributed in the west African country of Ghana through the government's adult education program.
Eyejusters. Eyejusters is a small technology company in Oxford that was founded to bring low-cost eyewear that incorporates the company's SlideLens adjustable lens technology to the developing world.
Eyejusters self-adjustable eyewear (see closeup).
Though Eyejusters is a private company and is not affiliated with the Centre for Vision in the Developing World, several members of its management team are friends of Dr. Silver and were involved in CVDW's Adspecs project.
Eyejusters' SlideLens technology is similar to the Adlens two-plate Alvarez adjustable lens system. The powers of the lenses are determined by how the individual lens plates 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.
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 July 2014]
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