Thanks to continual advances in hard coatings, today’s lenses are more durable than ever before. But are they tough enough?
That depends on your definition of toughness. For consumers, lens toughness, or durability, is defined by the terms of the lens manufacturer’s warranty. Most warranties cover a lens for one or two years, or for the life of the patient’s prescription, which is only two years in many states. But the length of a warranty is also based on the fact that most hard coatings, even the better ones, deteriorate after a couple of years.
That raises some questions. Are manufacturers willing to push the envelope of lens durability, or are they content with the status quo, which amounts to planned obsolescence? Assuming better hard coatings can be developed, how long would we want lenses to last? Five years? Forever? And what implications does this have for labs, eyecare professionals and consumers?
Two recent developments in optical research point in the direction of extending lens life. One is that Essilor recently filed a U.S. patent application for “self-healing transparent coatings” for lenses made of standard plastic lenses, polycarbonate or other materials. No doubt the idea of owning a lens that could repair itself after being scratched or dinged would be very appealing to consumers.
The other development is new findings by scientists at MIT who were studying the shells of a sea creature, the mollusk Placuna placenta. The scientists discovered that these shells, which are exceptionally tough, have a specialized nanostructure with high optical clarity and high resistance to penetration and damage. The properties of this “natural armor” make it a promising template for the development of bio-inspired synthetic materials such as eye protection, the researchers said.
Although it’s unclear what will result from the Essilor and MIT research, it’s likely that tougher times are ahead for eyeglass lenses—or at least tougher coatings.
Group Editor, Lenses and Technology