Some years ago, Transitions Optical came up with the term “variable tint” to refer to the way their plastic photochromic lenses can adjust to changing light conditions. I always liked the term because it’s descriptive and sets their product apart from “fixed tint” lenses.

More recently, Transitions has pushed the variable lens technology envelope even further with the introduction of their Vantage variable polarized lenses. Both Vantage and other Transitions photochromic lenses achieve their variable effects through technologies that realign the molecules within the lenses.

Yet variable or adjustable lens technology isn’t just advancing on the molecular level. At least two companies, Superfocus, based in the U.S. and Adlens, based in the U.K., have introduced glasses with fluid-filled lenses that the wearer can mechanically adjust and focus. Adlens also markets glasses that feature an Alvarez lens system consisting of two lenses that the wearer mechanically slides into alignment to focus. Another U.K.-based company, Eyejusters, also markets glasses featuring a sliding lens focusing system.

In the emerging field of electro-active, adjustable eyewear, PixelOptics’ emPower “electronic focusing eyewear” offers distance and intermediate zones plus a reading zone that can be activated electronically when needed.

Electrochromic sunglasses are also intriguing, but so far no one has been able to successfully market the technology. One issue is battery size, another is cost. The technology is continuing to evolve though, so someone is bound to take another shot at it soon.

Variable lens technology in all of its forms—molecular, mechanical and electronic—is going to be increasingly important because it gives consumers new options, and companies such as Adlens and Eyejusters are providing low cost solutions for people in the developing world. Keep your eyes on this exciting and rapidly evolving category.

—Andrew Karp