What Are High Index Lenses? To understand what high index lenses are one must first understand how optics work in general. Light is bent when it passes through a lens. The amount by which the light is bent is determined by the thickness of the lens, which is determined by the prescription that is in the lens. The weaker the eyes, the more the lenses must bend the light, meaning the higher the prescription must be to provide clear vision. If you are nearsighted, the Sphere value of your prescription will have a minus symbol (-). The higher the minus power, the thicker the edges of your prescription lenses will be. This is where the high-index lens materials come in. There are now a variety of new plastic materials that bend light more than the conventional plastic used for eyeglasses. This means less lens material can be used to correct the same amount of nearsightedness.
Advantages of High-Index Lenses
Thinner: As a result of the ability to bend light more, nearsighted lenses made of high-index materials have thinner edges than the same prescription made from conventional plastic material.
Lighter: Less lens material is required than with conventional plastic, which reduces the overall weight of the lenses, so they're more comfortable to wear. High-index glass lenses also have thinner edges, but high-index glass is heavier than conventional glass, so there is not as much weight savings with glass as there is with plastic lenses.
The Higher the Number, the Thinner the Edges
