High Index Lenses

Compared to lenses made with CR-39 plastic or even polycarbonate, high index lenses are expensive. Because of their cost, it's only natural that you would want to keep your high index lenses for as long as possible. Of course, the same is true for the frame as well. The longevity of your high index eyeglasses comes down to your selection of protective coatings for the lenses, your frame selection, and your use and care habits.

Anti-Scratch Protective Coating

High index lenses are made from high-refractive-index polymers. In other words, they're made from plastics. Compared to glass, plastics are soft and have a poor scratch resistance. If you drop high index glasses, place them in the sand, or wipe grit from them with a dry cloth, you will likely scratch them. Over time, large and small scratches will accumulate on the lens surfaces
from past accidents and care mistakes. Scratches are not only distracting, but cloud your vision and produce glare when night driving.

Because accidents and mistakes are inevitable, it's worth the extra money to get anti-scratch coatings for your high index eyeglasses. These coatings resist scratches almost as well as glass, and will increase the useful life span of your lenses.

A Durable Frame

The durability of a frame will depend on its design and the material from which it's made. The cliché that a chain is as strong as its weakest link, applies to frame design. You can make a frame from a very strong material, but if the design is inherently weak, it won't have an exceptionally long life span.

An example of a weak design is rimless glasses.
While they do a good job of minimally impacting your appearance, they are relatively weak at the attachment points of the frame with the lens. A lot of mechanical stress gets concentrated at these points. And the frame can break there from abuse such as placing the glasses in a pocket or dropping them. A frame that completely encloses the lens rim is a stronger design. Note that rimless glasses can last a long time, but require a high level of care.

While there are a number of durable frame materials, two notable ones are nylon and flexon. Nylon is a lightweight plastic that's flexible and strong. Nylon frames are generally more flexible than those made of metal and are available in many colors. However, they aren't as strong as metal and are weakened by long-term exposure to sunlight. The chemical bonds within nylon also break down with age.

Flexon is a titanium nickel alloy metal that's also lightweight, flexible, and strong. What makes this metal unique is its ability to return to its original set shape after bending or twisting it. It essentially has a kind of built-in
"memory."

Proper Care

How you treat your glasses is a big factor in their longevity. Here are five important care tips:

Place your glasses in a case. Once there, you can put the case in a pocket or set it down on an abrasive surface without worry. Never place glasses directly in a pocket or lens down on any surface.
Never clean your glasses with a dry cloth. Run water over the lenses, use diluted dish soap, and then rinse. Use a microfiber cloth for drying them. Don't use solvents or harsh cleansers.
Keep your glasses off your head. Using your head as a prop for your glasses is an accident waiting to happen.
Use both hands when taking off your glasses. Grabbing your glasses by a single temple stresses the frame at the joints, and wear them out over time. Although grabbing your glasses by the nose bridge doesn't stress the frame, using one hand is less secure than using two.
Don't place your glasses in extremely hot or cold places. Plastics don't bear up well to extreme temperatures. Metals will expand or contract relative to the lenses, which causes damage.