(Phys.org) -- A new kind of eyeglasses is now available from a British company that allows the wearer to adjust the prescription anytime, anywhere, via small thumb-dials on the sides. Called, Eyejusters, the glasses make use of a technology called a Slidelens, which very aptly describes how these glasses do their magic. Each lens is actually two lenses that have slightly different shapes; turning the thumb-dial causes one lens to move slightly left or right and that changes the focal point for the wearer. The lenses are moved until the person doing the focusing finds the sweet spot; which is exactly how users focus a pair of binoculars.
The web site for the Eyejusters says their main market is the developing world, where a lot of people with vision problems cant afford to see an eye doctor, much less the glasses that would be prescribed. Eyejusters solve both problems; when ordered, they come with an eye-chart that can be used to help discern if a persons vision can be corrected with Eyejusters (the power range is from +4.5 to 0 D (positive) and 0 to -5.0 D (negative)) and to figure out which version they need (for near or far vision correction).
The glasses were developed by four guys; Dave Crosby, Owen Reading, Richard Taylor and Greg Storey, who found a common interest in self-adjustable glasses and in the process created a company to fulfill the goal of providing low cost eyeglasses to the millions of people the world over who cannot afford a traditional pair. Their secondary market is for people who could use adjustable glasses for other than general use purposes, such as reading, working on a computer, knitting, i.e. for people as they get older and find they have trouble focusing while performing different tasks.
The Eyejusters, which come with detachable thumb-dials also come with a plastic case and special cleaning cloth. The cloth can be used to clean both sides of both lenses because the outer lens can be hinged down for easy access. The Eyejusters also offer UV protection, which has been incorporated to help prevent eye damage from the sun, another common problem in underdeveloped countries.
Another interesting aspect of the adjustable glasses is that it appears with a little tweaking, they could be used to perform self exams in more developed countries. By adding a digital display, the wearer could work out their own prescription and send it to a company that sells traditional eyeglasses, sidestepping an expensive trip to an ophthalmologist.
Explore further: Physicist's vision for helping world's poor: self-adjusting eyeglasses