Choosing a frame that fits both your face and your lifestyle is important when buying a new pair of glasses, but the most important consideration for new glasses is the type of lens. When buying glasses there are four factors to consider: appearance, comfort, vision, and safety. While the frame affects both appearance and comfort, the lenses affect all four factors. When buying new glasses,it is important to consider lens materials and how they fit with your lifestyle.At A1AOptics we take the time to sit with you and determine what type of lens material will work best for your chosen frame and your lifestyle.
Below is a short guide to the types of lens materials available to give you what you need to know when choosing new lenses. This guide covers all types of prescription lenses including single vision and multifocal lenses such as progressives or bifocals
Glass Lenses
Until the second half of the twentieth century all glasses lenses were made from crowned glass. Glass lenses have exceptional optical properties which gives the wearer the clearest, sharpest vision through their glasses. There are, however, some drawbacks to glass lenses. For one, glasses are heavy. Heavy lenses can become uncomfortable when wearing glasses for an extended period of time. More important to consider, glass lenses are fragile, making them prone to break. This is a headache if the glasses are dropped but is particularly concerning in the event the lenses are impacted by an object while the person is wearing the glasses. For these reasons, glass lenses are rarely used in the optical industry these days.
Plastic Lenses
During World War II high strength plastic polymers were developed for various military applications.One of these polymers, CR-39, offers excellent optics and is about half the weight of glass. Originally developed for use in lightweight external fuel tanks for airplanes during the war, CR-39was introduced to the optical industry shortly after the war ended. CR-39 is lighter and also more impact resistant than glass. These properties, combined with the relatively low cost of the polymer, make CR-39 a popular choice for eyeglass lenses even today.
Polycarbonate Lenses
Originally developed for high impact applications such as bullet-proof windows for banks, polycarbonate lenses have become increasingly popular in the eyeglass industry. Today the majority of lenses in sunglasses and many prescription eyeglasses are made from polycarbonate.The optics of polycarbonate are not as good as CR-39 or glass, but it is much lighter and superior in terms of impact resistance. Because of this, polycarbonate is preferred for children’s eyeglasses and for safety glasses
Trivex Lenses
Trivex lenses, introduced in the early-2000s, are thinner than polycarbonate lenses and offernearly the same amount of impact resistance. In addition to being lighter weight, Trivex lensesoffer better optics than polycarbonate
High-Index Plastic Lens
Over the last couple of decades lens manufacturers have worked to produce thinner, lighter weight lenses. These efforts have resulted in the introduction to high-index plastic lenses. These lenses are thinner and lighted than CR-39 lenses and offer better optics than polycarbonate, although the impact resistance is not as good.
Here are popular eyeglass lens materials, arranged in order of refractive index and lens thickness (pretty good indicators of cost). Lenses are listed in order of thinnest to thickest. Except for the crown glass, these are all plastic materials. This table also indicated Abbe Value. In general, the higher the Abbe Value of a lens material, the better the optics of that lens will be.
| Lens Material | Refractive Index | Abbe Value | Key Features and Benefits |
| High-index plastics | 1.70 to 1.74 | 36 (1.70) 33 (1.74) | The thinnest lenses available. Block 100 percent UV. Lightweight. |
| High-index plastics | 1.60 to 1.67 | 36 (1.60) 32 (1.67) | Thin and lightweight. Block 100 percent UV. Less costly than 1.70-1.74 high-index lenses. |
| Tribrid | 1.60 | 41 | Thin and lightweight. Significantly more impact-resistant than CR-39 plastic and high-index plastic lenses (except polycarbonate and Trivex). Higher Abbe value than polycarbonate. Downside: Not yet available in a wide variety of lens designs. |
| Polycarbonate | 1.586 | 30 | Superior impact resistance. Blocks 100 percent UV. Lighter than high-index plastic lenses. |
| Trivex | 1.54 | 45 | Superior impact resistance. Blocks 100 percent UV. Higher Abbe value than polycarbonate. Lightest lens material available. |
| CR-39 plastic | 1.498 | 58 | Excellent optics. Low cost. Downside: thickness. |
| Crown glass | 1.523 | 59 | Excellent optics. Low cost. Downsides: heavy, breakable. |