When purchasing glasses today, there are a wide variety of choices. The most basic choice is between traditional glass lenses and newer plastic lenses, such as those made from polycarbonate. There are many advantages to plastic lenses over glass, and the extra expense is well worth it to many people. Plastic lenses are far lighter than glass, making them less likely to slip down your nose, especially in stronger prescriptions. Heavy glass lenses also leave indentations on the nose, while plastic lenses sit much more lightly. Plastic lenses are impact resistant, making them a better choice for children, active adults, sportswear, and safety wear. It takes a far greater force to break a plastic lens than a comparable glass lens, and while glass shatters, plastic will more likely dent, or if the force is great enough, crack without shattering. Perhaps the most appreciated feature of plastic lenses is that they can be thinner than glass lenses. Those with strong prescriptions know how thick glass lenses can distort the face. Thick nearsighted lenses significantly reduce the size of the eyes, detracting from the natural appearance of the wearer. A nearsighted lens is also wider at the edges than in the middle, making the edges noticeable in fashionable wire frames or frameless glasses. A thick farsighted lens is wider in the middle and narrow at the edges. The wide middle magnifies the eyes, resulting in an “owlish” look. For people with strong prescriptions, high index plastic lenses are a great choice. These plastic lenses can be thinner, because they bend more light than glass or normal plastic. High index plastic lenses can virtually serve the strongest prescriptions without distorting the face, and they look attractive in any frame. No one will ever guess how strong your prescription really is! High index plastic lenses are the most expensive lenses available, but to those who benefit, they are worth every penny. If you have struggled with “coke bottle glasses” or have forgone glasses in certain situations, embarrassed by how they made you look, you will likely loves these lenses. For those with little correction, normal plastic lenses will deliver all of the benefits of plastic at a lower cost than high index lenses. Special coatings make plastic lenses scratch-resistant, and an optional anti-reflective coating makes the lenses more transparent than glass, passing over 99% of all light. Plastic lenses can also be anti-glare, and they reduce harmful ultraviolet (UV) rays better than glass. High index glass lenses are also available, but the material is heavier than normal glass, so even though the lenses are thinner, they are not significantly lighter. These might be a good choice for inactive adults or seniors with strong prescriptions who would like to improve their appearance but do not wish for a lighter or more durable lens. If your prescription is weak and you are not active, traditional glass lenses will be less expensive than their plastic counterparts. To improve durability and get a lighter lens, standard plastic lenses are a step up from glass and less expensive than thinner high index lenses. Source
