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What Are High-Index Lens Glasses?

Any lens material with a refractive index higher than plastic or glass (1.50, 1.52) is considered high index. High-index glasses weigh less and provide more comfort than ordinary glasses, as well as being considered a more attractive option to thicker glass lenses. High-index lenses are especially recommended for people with strong eyeglass prescriptions for farsightedness, nearsightedness or astigmatism according to All About Vision.

  1. How They Work

    • High-index lenses refract light more efficiently than glass. Nearsightedness and farsightedness is due to the inability of the eyes to refract light properly. Eyeglass lenses aim to correct refractive errors by refracting light as it passes through the lens. However, when the nearsightedness or farsightedness is particularly severe, the amount of glass or plastic required to correctly refract the light is quite large. High-index lenses use less material to refract light correctly, resulting in thinner lenses.

    How They Differ From Ordinary Lenses

    • Ordinary lenses are made from glass or conventional plastic. People with strong nearsightedness and farsightedness require thicker, heavier lenses due to the limitations of glass or plastic lenses to refract light. The efficiency with which a material refracts light is measured by refractive index. The refractive index of glass is 1.52, and for most plastic lenses it is 1.50. High-index lenses typically range from 1.53 to 1.74.

    Advantages

    • Because high-index lenses bend light more efficiently, they have thinner edges than lenses with the same prescription made from conventional glass or plastic. This results in a thinner, lighter lens, and therefore a lighter pair of glasses. Heavy, thick lenses can also be uncomfortable or bulky, with the increased weight putting pressure on the bridge of the nose. With high-index lenses, you can avoid this discomfort.

    Variety

    • High-index lenses now come in a variety of designs. These include bifocal and trifocal lenses, progressive lenses and photochromic lenses. Bifocal and trifocal lenses have multiple lens powers in one lens. Progressive lenses are bifocal and trifocal lenses with no visible lines between the lens powers, for a smoother aesthetic. Photochromic lenses darken upon exposure to sunlight. Ask your eye doctor or optician for further details.

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