Focus on Fundamentals

The term “photochromic” refers to a technology, not a material.

Thanks to chemical responses to ultraviolet light, photochromic lenses turn dark in sunlight and become clearer indoors, where they are exposed to less UV light.

Outdoors, they provide 100% protection against the UV rays.

Until recent developments, these lenses didn’t darken behind the windshield of a car. Today, several brands now offer photochromic lenses that boast this feature.

Photochromic lenses also block blue light, protecting eyes from that harmful light emitted by the sun.

THEN AND NOW

Photochromic lenses were developed and patented in the 1960s at Corning Glass Works in Corning, NY. The company launched Bestlite glass lenses in 1965 and Photogray glass lenses three years later.

Fast forward to the introduction of plastic lenses in the 1980s and then to 1990, when Transitions lenses were launched through a joint venture between PPG and Essilor.

The technology has continued to evolve ever since. The latest iteration includes lenses in several colors (indoors and out) and for a variety of applications. They’re available in multiple materials, including high index and polarized, and in every conceivable design.

Many manufacturers now market them. Some utilize an imbibe technology, meaning photochromic molecules are imbibed onto the lens surface. Others use in-mass technology in which the photochromic molecules are evenly dispersed throughout the lens.

The technology was previously exclusive to spectacle lenses, but a photochromic contact lens became available in 2019. Acuvue Oasys with Transitions was developed by Johnson & Johnson Vision in partnership with Transitions Optical.

HOW THEY PERFORM

Photochromic lenses work via a chemical reaction in the lenses. A few different methods—including the use of proprietary dyes, silver chloride, and copper chloride—are utilized.

How does chloride work? Trace amounts of silver chloride, when exposed to UV light, become silver metal. This allows the lens to absorb visible light and turn darker. Copper chloride, on the other hand, helps the lenses return to their non-absorbing state when no longer exposed to UV.

Photochromic lenses also protect wearers from blue light both indoors and outdoors. That’s especially important in today’s age of digital devices.

WEARER BENEFIT

What else? Photochromic lenses are excellent for anyone who goes from indoors to outside often and for both children and adults who participate in outdoor activities.

Thanks to their glare-reduction properties that can help reduce eye strain, they’re increasingly selected as an everyday lens. They’re also a great choice for people who are sensitive to light.

Photochromic lenses produce different results depending on the manufacturer. For example, some transition faster than others in response to changing light. They also vary in terms of the color residue remaining on the lenses when in the inactivated state indoors.

Photochromic lenses are an exciting option for wearers both indoors and out. That’s why Los Angeles-based optician Jennifer Centeno always demos them in both places. “Outside, patients get to see the lenses in real time—and watch as mine change to whatever color I’m wearing. It sparks a conversation that’s often like, ‘Your lenses are so cool. I need to have them.’”