Indexes and thicknesses

The material selected for a lens is fundamental, as it determines both comfort and clarity of vision.

The material selected for a lens is fundamental, as it determines both comfort and clarity of vision.

It’s commonly believed that the greater the correction, the thicker the lens, but this isn’t exactly how it works. 

To be sure you’ve chosen just the right lens, you need to take various factors into account, such as lifestyle, workplace, home environment, and the frames of your eyewear.

You often don’t need the thinnest lens if your frame doesn’t require it. In the same way, you shouldn’t be too set on a specific type of frame if it isn’t right for the lens that is best suited to your needs.

Eyewear frames are typically divided into the following categories:

  • Rimless (or "glasant"): These frames feauture a bridge, nose pads, and temples with related hinges attached to the lenses by way of screw or pins. Holes or grooves are cut into the lenses.
  • Semi-rimless (or “nylor”): Half way between rimless and full-rim frames, semi-rimless frames support the upper part of the lens with a metallic or plastic material, while the lower portion is held up by a nylon thread fed through a groove cut into the lower edge of the lens.
  • Full rim: These are the most traditional frames and come in a range of materials (e.g. acetate, metal, titanium alloys) and shapes.

These are the main materials DIVEL ITALIA and other manufacturers use to make lenses:

- MINERAL – This refers to traditional glass, which is less common than it once was because it is both highly fragile and heavier than lenses made from “organic” materials. Nonetheless, these lenses may still be found on the market because of their high degree of scratch resistance. 👍PROS: scratch resistance. 👎CONS: fragile 

- ORGANIC – Plastic lenses, such as the CR 39, are the most common type of lens. They are more common than mineral glass because they are thinner, lighter, and more resistant. They also provide high-quality vision thanks to the range of refraction indexes available. The CR 39 is the best suited to being tinted due to its limited color dispersion. 👍PROS: lightweight, high performance. 👎CONS: require protective treatments. 

Most lenses on the market today are made of an organic material, not mineral glass. Each type of material corresponds to a different refraction index. The higher the index, the thinner the lens.

DIVEL ITALIA provides lenses in the following materials:

  •  Ind. 1.50 (classic CR 39). Our 1.500 material has excellent optical qualities thanks to its particularly high Abbe number(58). It is suited to all colors and mirror types and is two times lighter than a traditional mineral lens. Glasant: * Nylor: ***** Full rim: *****
  • Ind. 1.56 . Our 1.560 material is 20% thinner than a standard lens (ind. 1.500 CR-39) and can be produced in any color tone or intensity up to a maximum of 75%. It is suited to low and mid-range prescription strengths. Also available in FOTOCOLOR and FOTOCHROMA. Glasant: - Nylor: - Full rim: *****
  • Ind. 1.60. Our ind. 1.600 material is 30% thinner than a standard lens (ind. 1.500 CR-39). It is the most recommended for any type of frame, and its high Abbe number makes it comfortable in all optical situations. Glasant: ****** Nylor: ***** Full rim: *****
  • Ind. 1.67. Our ind. 1.670 Aspheric is 40% thinner than a standard lens (ind. 1.500) and can be produced in any color tone or intensity up to 75%. It is recommended for all frame types and is particularly suited to glasant rimless frames. Glasant: **** Nylor: **** Full rim: *****
  • Ind. 1.70. 1.710 Aspheric SILKEN LASER-THIN is our new material with a refractive index of 1.710 and super-thin, aspheric design. Falling between our 1.670 and 1.740 index lenses, it unites the best of both worlds in terms of versatility, efficiency, cost, and aesthetics. Our 1.710 LASER-THIN lenses feature an aspheric geometry in order to ensure minimal thickness even at higher prescription strengths (45% thinner than a standard 1.50 CR-39). On a par with our 1.740 lenses, the high refractive index ensures superior aesthetics compared to lower indexes while maintaining the excellent versatility of 1.670-index lenses. Glasant: * Nylor: ***** Full rim: *****
  • Ind. 1.74. Our 1.740 Aspheric material is the thinnest shatter-resistant lens on the market. In high prescription strengths, it noticeably reduces the eye-magnification effect thanks to its very high refractive index. It is 50% thinner than a standard lens (ind. 1.500) and three time thinner than a high-index mineral lens. Glasant: - Nylor: ** Full rim: *****

- POLYCARBONATE – This highly resistant, resin-based material is most commonly used for sports eyewear because of its light weight and high impact resistance. It also provides full protection from UV RAYS. 👍PROS: impact resistance. 👎CONS: vision quality is not comparable to that of other materials.

- SPECIAL MATERIALS – Our special materials include Fotochroma. Divel Italia photochromic lenses come in six fashion colors (green, gray, pink, purple, brown and blue) with an index of 1.56 as well as in gray with an index of 1.61. The particular characteristic of photochromic lenses is that they are able to react to changes in lighting conditions, darkening or lightening with changes in light. These lenses are suited for people who often have to go back and forth from indoors to outdoors. 👍PRO: avoid changing glasses. 👎CONS: difficult to choose the color, you will want to have them all! 

- ECO MATERIALS – Divel Italia’s 🌱GREEN LINE is an environment-friendly plastic made from 40% bio-material that ensures excellent visual performance. It is currently available for sunglasses and is being tested for corrective lenses. Nylon eco.👍PROS: eco-friendly. 👎CONS: the coatings can slightly decrease the percentage of organic material.