Perhaps you've never thought about it, but eyeglass lenses can be made from different materials. The information below highlights your options -- and why you might consider requesting a particular material for your next pair of eyeglasses.
Plastic
Plastic lenses are much lighter and less breakable than glass lenses. Traditional plastic lenses are made from a hard resin that is cast or molded in the wet state into lens blanks. These plastic blanks can be ground into specific shapes to fit any lens frame. The most common plastic lens material is called CR-39.
High index
High index is an advanced material that provides significant advantages over traditional plastic or glass lenses. High-index lenses are:
- Thinner, so you'll have slimmer glasses and can choose from a wider choice of frames
- Lighter, so your glasses weigh less and you'll feel more comfortable
- Flatter, so your lenses will bulge less from the frame (and if you are farsighted, your eyes will appear less magnified and more natural in size)
High-index refers to the lens material's index of refraction, or the degree to which it refracts light. The higher index of refraction enables the material to bend light to a greater degree, so less curvature is needed in the lens to achieve a specific prescription power. Because less material is required to produce the lens, lenses are lighter. High-index materials are available in hard resin plastic and extra impact-resistant polycarbonate plastic. There are also high-index glass materials.
Glass
Glass was the first material used to make eyeglass lenses. While glass can provide remarkably good vision correction, it's heavy and breakable.
Polycarbonate
For maximum impact resistance, polycarbonate is the lens material of choice.
Polycarbonate lenses are ten times more impact resistant than conventional plastic or glass lenses. While impact resistant does not mean shatterproof, polycarbonate lenses can give an extra level of protection to lens wearers who have active lives or participate in sports. Polycarbonate is the material preferred for children and teenagers—as well as people who work in certain manufacturing occupations. In addition to its impact-resistant qualities, polycarbonate is thinner and lighter than conventional plastic or glass lenses—and it comes with built-in ultraviolet protection.
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