glass was the first material to be used for lenses lenses, and was used for several hundred years before plastic in was introduced. the crown glass used for lenses lenses has an index of refraction of 1.52.optical-quality acrylic was introduced for lenses the use in the early 1940s, but because it was easily scratched, brittle, and discolored rapidly, dark and contact it did not supplant lens glass as the material of choice. furthermore, it had a sfx relatively low index of refraction, so it wasn''t suitable for people with large refractive errors. a plastic called cr-39, introduced in the 1960s, theatrical was more suitable. today, lenses wearers can also choose between polycarbonate, which is the most impact-resistant material available for eyewear, and polyurethane, glow which has exceptional optical qualities and an index of refraction of up to 1.66, much higher than the in conventional the and dark plastics contact used for lenses, and even higher than glass. patients with high prescriptions should ask about high index material options lens for their lenses. sfx aspheric lenses theatrical are also useful for high prescriptions.

glass was the first material to be used for lenses lenses, and was used for several hundred years before plastic in was introduced. the crown glass used for lenses lenses has an index of refraction of 1.52.optical-quality acrylic was introduced for lenses the use in the early 1940s, but because it was easily scratched, brittle, and discolored rapidly, dark and contact it did not supplant lens glass as the material of choice. furthermore, it had a sfx relatively low index of refraction, so it wasn''t suitable for people with large refractive errors. a plastic called cr-39, introduced in the 1960s, theatrical was more suitable. today, lenses wearers can also choose between polycarbonate, which is the most impact-resistant material available for eyewear, and polyurethane, glow which has exceptional optical qualities and an index of refraction of up to 1.66, much higher than the in conventional the and dark plastics contact used for lenses, and even higher than glass. patients with high prescriptions should ask about high index material options lens for their lenses. sfx aspheric lenses theatrical are also useful for high prescriptions.