Overcast sky in the morning, neon lights at work, glaring sunlight in the afternoon and dimmed light in a restaurant in the evening. The lighting situation and general conditions experienced by your eyes change many times in the course of the day. This means you have to keep taking off your glasses or, if required, put on your sunglasses — which may not have the proper or even no prescription. The result: eyestrain — a problem that can be avoided. New, rapidly self-tinting lenses from Carl Zeiss combine prescription power with effective light protection and therefore make it unnecessary to switch to another pair of glasses in many situations.
The idea of developing one pair of glasses for all situations and lighting conditions is something that has occupied optical specialists for a long time now. As far back as the 1960s, the chemists Stanley Donald Stookey and William Armistead invented the first photochromic eyeglass lenses to react to UV radiation. Since then, a lot of improvements have been made to the quality and performance of self-tinting lenses. The reaction speed of the latest lenses is high enough to enable comfortable vision in all light conditions. In a matter of seconds the lenses darken in bright sunlight to just ten percent transmission and clear again in cloudy weather or indoors within an extremely short time. Photoactive color molecules regulate this process. When the molecules are exposed to UV radiation, they expand and cause the lens to darken. The stronger the UV radiation, the darker the lens becomes, and vice-versa. In other words, they make the need to keep changing your glasses in altering light conditions a thing of the past.
June 1, 2011