High Index Lenses: These lenses are designed to be noticeably thinner and lighter compared to glass, CR-39 (hard resin), and other plastic lenses. They allow the wearer to avoid having “coke-bottle” lenses. There are different types of high index lenses, most of them are classified by a number. In general, the higher the number, the thinner and lighter the lens is. Aspheric + High Index Lenses: Combining these two lens options creates a lens that is noticeably lighter, slimmer, and thinner.
High-Index includes 1.60, 1.67, and 1.74. These lenses are thinner than mid-index, glass, or plastic lenses.
Mid-Index includes 1.54, 1.56, and 1.57. These lenses that are thinner than glass but not as strong as CR-39.
Polycarbonate Lenses: These lenses are thin and light with enhanced impact resistance compared to plastic lenses (10x more). They are commonly used in safety eyewear, sports eyewear, and children’s lenses. However, they can scratch easily therefore a scratch-coating is advised.