How Thinned down lenses work
High-index eyeglass lenses are the right choice if you want thinner, lighter lenses and eyeglassesthat are as attractive and comfortable as possible.
Thinner, lighter high-index lenses are especially recommended if you have a strong eyeglass prescription for nearsightedness, farsightedness or astigmatism. But high-index lenses can make your eyeglasses noticeably slimmer, lighter and more attractive regardless of how strong your prescription is.
How High-Index Lenses Differ From Regular Lenses
Eyeglass lenses correct refractive errors by bending (refracting) light as it passes through the lens. The amount of light-bending ability (lens power) that’s needed to provide good vision is indicated on the eyeglass prescription provided by your eye doctor.
The difference a high-index lens material can make: the same correction for nearsightedness in regular plastic lenses (left) vs. high-index lenses (right). Images: Essilor
Refractive errors and lens powers required to correct them are measured in units called diopters (D). If you are mildly nearsighted, your lens prescription might say -2.00 D. If you are highly myopic, it might say -8.00 D.
If you are farsighted, you need “plus” (+) lenses, which are thicker in the center and thinner at the edge.
Regular glass or plastic lenses for high amounts of nearsightedness or farsightedness can be quite thick and heavy. Fortunately, chemists have created a variety of new “high-index” plastic lens materials that bend light more efficiently.
This means less material can be used in high-index lenses to correct the same amount of refractive error, which makes high-index plastic lenses both thinner and lighter than conventional glass or plastic lenses.
Advantages of High-Index Lenses
Thinner. Because of their ability to bend light more efficiently, high-index lenses for nearsightedness have thinner edges than lenses with the same prescription power that are made of conventional plastic material.
Lighter. Thinner edges require less lens material, which reduces the overall weight of the lenses. Lenses made of high-index plastic are lighter than the same lenses made in conventional plastic, so they’re more comfortable to wear.