Photochromic Lenses
Photochromic Lens Technology

Photochromic Lens Technology, How it works: The result of years of research and development, today�s photochromic lenses are the product of highly-sophisticated technologies. In its most basic form, a photochromic lens changes color because of a chemical reaction. When someone wears photochromic lenses outside, exposure to UV causes the lenses to darken. Indoors, at night, or on cloudy days there isn�t as much UV to cause the chemical reaction. Therefore, the lenses remain relatively clear.

Different photochromic manufacturers use different technologies to make their lenses � with separate and unique results. Photochromic lenses incorporating surface technology rely on organic photochromic dyes �imbibed� into the surface of clear plastic lenses. The imbibed process draws the photochromic molecules into the lens surface to a depth of 0.15mm.

Imbibed Technology

Late in the 1990�s, a different technology for making plastic photochromic lenses emerged. Using a photochromic technology similar to glass lenses, Corning introduced a new patented plastic lens material in which photochromic molecules are dispersed evenly throughout the mass of the lens. This new technology for plastic photochromic lenses is called �in-mass�.

Density, refractive index and ABBE value of an in-mass lens is dependent on the lens material. Rodenstock and Hoya produce in-mass photochromic lenses, but the most popular in-mass lens in the U.S. is Corning�s SunSensors lens. For this reason, for the balance of this course the in-mass lens we�ll refer to is Corning SunSensors. For imbibed technology lenses, we�ll be referring to Transitions 1.50 index lenses.

In-Mass Technology