Eyeglass lenses come in many different materials and styles. The type of lens you purchase depends on your prescription and how you use your glasses. The quality of lens materials and coatings is usually reflected in price.
The first optical lenses were made from glass. Glass gives the clearest vision and is the most scratch-resistant of all the lens materials but glass is the heaviest.
Plastic lenses are a good value if you want a lightweight lens. Plastic is lighter and also more shatter-resistant than glass.
Polycarbonate lenses are also light and are the most shatter-resistant lenses available. Polycarbonate lenses are the only type of lenses recommended for children because the lenses are less likely to break than plastic or glass. Polycarbonate usually costs more but is a good value option for lens safety.
High-index lenses are specialty prescription lenses that are compressed to make your lenses lighter and thinner. This type of lens is valuable if you have really thick lenses. Index refers to index of refraction and the higher the number, the thinner, lighter and more expensive the lens. Your eye care professional helps determine the best high-index lens based on your prescription.
Lens coatings can be added to lenses to make them more scratch-resistant, filter ultraviolet light, add color to the lenses and reduce glare. Coatings usually cost more but increase the value and quality of lenses.