Photochromic lenses have been an important part of the ophthalmic community since glass photochromic lenses were introduced in the 1960s. Although inordinately expensive compared to conventional lenses available at the time, glass photochromics were well accepted by the profession and the public. Later, when sales of glass lenses began declining as plastic lenses became more viable, photochromic glass lenses shored up glass sales -- soon accounting for half of all glass lenses dispensed in this country.

The advantages of photochromic glass were extended in the 1990s, when Corning introduced a new photochromic glass called Thin & Dark�. Designed as a true sunglass, Thin & Dark provided two major advantages over what was previously available in glass. The material's formulation permitted surfacing lenses to 1.5mm thick, thereby substantially reducing the weight of the lens. The new lenses also darkened considerably more than other photochromics.

Meanwhile, in 1991, the first Transitions plastic photochromic lens became available, and suddenly the entire field of photochromic lenses took on a new life. Now, only eight years later, more than 16 percent of all lenses currently sold in the United States are photochromic.

In fact, most lens manufacturers now feature photochromic plastic lenses in their product lines, and these manufacturers, and eyecare professionals as well, have come to count on the profits generated by these popular "magic" lenses.

In view of such incredible growth, the logical question now is: Can those profits continue, or is interest in photochromics declining?

In fact, there's even more activity on the part of vendors than ever before. That's why we picked this issue to review the current state of photochromic lenses, including logical estimates of what the future holds for this important lens category.

Growth Factors

Double-digit sales increases of photochromic lenses during the last few years resulted from two factors, both involving tremendous investments on the part of Transitions Optical.

Getting the word out. The first was that during this period, consumers were discovering -- thanks in no small part to the unprecedented investment in consumer advertising on the part of Transitions -- that lenses that darkened in the sun were now available in lightweight plastic.

Consumers had wanted this for years. A steady increase in sales of photochromic lenses resulted, prompted by that long-term, pent-up consumer desire for lightweight changeable lenses.

Continual improvements. Another factor, however, also had an influence during the past eight years. This was the continuing improvement in the product itself.

During that period, for example, Transitions introduced three different versions of its photochromic lens, each one a substantial improvement over previous technology. For years, Transitions has closely tracked an important concern in consumer surveys of Transitions wearers. Wearers were asked, "Will you order Transitions lenses again the next time you purchase eyewear?" Answers to that question, in large part, have been positive, indicating customer satisfaction with changeable lenses.

Because Transitions had consistently introduced technical advancements, when a wearer of plastic photochromic lenses returned for an eye exam, the doctor or dispenser would inform them that an improved version of the Transitions lens was available. This was usually enough to encourage the patient to reorder photochromic plastic lenses.

The worldwide success of Transitions photochromic lenses firmly established one fact: There is a broad market for lenses that darken in the sun.

Inevitably, this produced competition. Seiko introduced a photochromic plastic lens called Changers� and Rodenstock also developed a series of photochromic lenses that were introduced to the U.S. market several years ago. In 1998, Transitions sued Rodenstock, claiming the Rodenstock technology infringed on a Transitions patent. In an amicable settlement, Rodenstock agreed to withdraw those photochromic lenses from the American market by December 31, 1998.

This was done, but then in the spring of 1999, Rodenstock introduced Color-Matic Extra, a new line of photochromic lenses based on a different technology. Their new photochromics will be available this summer in single vision, bifocals, and progressives.

Two Approaches

There are two basic ways to create plastic photochromic lenses:

Imbibition. Transitions developed a clever process in which the lens manufacturer produces a clear plastic lens (using a PPG plastic monomer related to CR 39).

Clear lenses are shipped to the Transitions plant where they undergo a process called imbibition. The process itself is complex and involves embedding photochromic properties in the front surface of finished or semi-finished blanks. It is not a coating, since the photochromic molecules actually migrate into the front surface. The best definition of "imbibe" is "soaking or saturating." Following the imbibition process, a hard coat is applied.

Because the darkening chemicals are only in the front surface, all Transitions lenses darken uniformly, regardless of lens power.

In photochromic glass lenses, darkening takes place throughout the material. As a result, plus lenses darken more in the center than at the edge.

Body casting. The plastic photochromic process used by other manufacturers produces photochromic lenses in a totally different manner. They use a process called "body casting" or "en masse" -- a process in which the photochromic properties are distributed throughout the mass of the lens.

Body-cast photochromic lenses do not require the manufacturer to ship lenses to a third party for treatment. Body cast or en masse lenses have photochromic dyes distributed throughout the lens, but the lenses still darken uniformly, regardless of power.

The reason for uniform darkening is that, unlike glass photochromics, UV light activating the darkening only penetrates the top layers of a body cast lens.

New Product Launches

The new photochromic series introduced by Rodenstock is based on the body cast manufacturing process. So is the process used by Optical Dynamics, a company that has produced a new in-office lens casting process for providing photochromics. It offers customers a photochromic monomer called Phases�, thus enabling them to cast both conventional and photochromic lenses. And Hoya reports it will be introducing a new product as well.

Another new development in the evolution of photochromics was revealed in the fall of 1998 when Corning, the first company to create a photochromic lens, though in glass only, announced it had perfected a new photochromic plastic for ophthalmic lenses, utilizing the body cast process.

Corning does not manufacture lenses, but produces raw materials -- until now, only glass -- that it sells to lens manufacturers. A similar distribution system is planned for its new photochromic monomer.

Simultaneously with its announcement, Corning acknowledged the filing of a lawsuit against Transitions Optical. The Corning action does not involve patent litigation over technology issues, but is a restraint-of-trade suit concerning their new photochromic plastic monomer. The company reports that it is planning on showing the lens at Vision Expo West in
Las Vegas.

One sure result of these continuing developments is that the entire photochromic field is heating up.

Will the growth seen this decade by Transitions continue within the category? There will certainly be increasing competition as more players enter the arena.

For example, Rodenstock is making strong claims for its ColorMatic Extra lenses, stating they darken faster and even partially darken inside an automobile, something no lens has accomplished in the past. The new Corning product is an unknown, but the initial reaction of many of those who have seen the lens has been encouraging. And, you can be sure that a company as dynamic and market-oriented as Transitions will not simply stand by and give up its hard-fought leadership role.

In fact, one advancement in Transitions technology has been the nationwide release of Transitions Polycarbonate lenses. Adapting the technology to a completely different material such as poly was a daunting challenge, but the difficulties have been overcome, and Transitions is currently in a national campaign to publicize this newest changeable lens.

Increased competition at this, the high end of ophthalmic lenses, will inevitably benefit the entire industry. Best of all, the end recipient of the improved technology will be those who wear the lenses -- your patients. EB