Want thinner, lighter lenses? Choose a high index lens material.
Nearly everyone can benefit from thinner, lighter lenses. High index lenses can be up to 50% thinner than regular glass or plastic lenses, and they're usually much lighter, too.
Though these lenses are especially beneficial if you have a strong eyeglasses prescription, they can make a noticeable difference in the appearance of virtually any pair of glasses. High index lenses bend light more efficiently than regular glass or plastic lenses, so less lens material is required to correct your vision.
Various high index lenses are available today in different price points based on how much thinner they are compared to regular plastic lenses. The lenses are classified by their "index of refraction" (or "refractive index").
Generally, lenses with a higher index of refraction will be thinner (and usually more expensive) than lenses with a lower index. The index of refraction of regular plastic lenses is 1.50. The refractive index of high index plastic lenses ranges from 1.53 to 1.74. Those in the range of 1.53 to 1.59 are about 20% thinner than regular plastic lenses, whereas 1.74 high index lenses are about half the thickness of regular plastic lenses.
Most popular lens designs (single vision, bifocal, progressive, photochromic, etc.) come in high-index materials, and your doctor or optician will know which ones are available in your prescription. Bifocal and trifocal high index lenses are also available, though the selection is more limited.
Note: High index lenses reflect more light than regular glass or plastic lenses, so anti-reflective (AR) coating is highly recommended for these lenses.