High Index Plastic Lenses: Abbe Number and Color Aberration

Abbe number is a very important and often-overlooked lens quality that is particularly relevant for high index plastic lenses.

Abbe Number and Color Aberration

A general rule of thumb when it comes to lens materials is the higher the index, the denser the lens. As lenses become denser and more efficient at bending light (which is what high index means), you start to get some undesirable side effects of the dense material. One is reflections, which is why it is important to get anti-reflective coating on high index lenses. The other is color aberration, which is the extent to which the lens blurs or “rainbows” colors, especially in the periphery.

  • Abbe number is a lens’s rating for color aberration. The lower the Abbe number, the worse the aberration is. Most lenses have an Abbe number between 30 and 90, with high index lenses generally falling between 30 and 60.
  • Color aberration is the extent to which a lens blurs colors. We’ve all seen the rainbows that are produced when white light passes through crystal and diamond. These rainbows are a form of color aberration; the crystal or diamond is so dense that it bends light in slightly different ways depending on the wavelength, or color, of the light. This happens to a lesser extent with many high index lenses.
  • In general, you can assume that, the higher the lens’s index, the lower its Abbe number will be, and therefore the worse its color aberration will be.
  • High index glass is infamous for having the worst color aberration properties, to the point that many people find they cannot wear glasses with high index glass material.
  • The high index plastic that is generally agreed to have the best balance between refractive index and color aberration is high index 1.70. This plastic’s color aberration is relatively low and its index is high enough to make most prescription lenses thin and light.
  • Aberration is something that some people can get used to and others can’t. It is a form of blurriness that streaks colors as opposed to lines.
  • Aberration is always worse in your peripheral vision than when you’re looking straight ahead.
  • Aberration in high index plastic is most common with 1.74 high index.
  • The thicker the lens is (the stronger your prescription is), the worse your aberration will be. Higher index lenses do make the lens thinner, but their aberration will still be worse than slightly thicker, lower index lenses.

Most people who get regular high index plastic lenses notice little to no color aberration. It is most common in 1.74 and all glass high index. If you are considering getting a very high index lens (above 1.70), it is worth considering whether you can deal with aberration. In extremely high prescriptions, color aberration can get bad enough in certain lenses (especially high index glass) that the optical clarity and usefulness of the lenses is compromised. If you are unsure which index is right for you, read some of our other articles, and hopefully you will find the lens you’re looking for!

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Guide to High Index Lenses 6 Responses to High Index Plastic Lenses: Abbe Number and Color Aberration
  1. [...] High index lenses come in a few varieties nowadays. In plastic alone, you have 1.67, 1.70, and 1.74. Glass comes in 1.80 and 1.90. As far as what's "better" is concerned, 1.70 is one of the most popular nowadays because it has low optical distortion (aberration) and is so close to the thinness and lightness of 1.74 that there is no noticeable difference. Glass high index is always thinner, but it's heavier than plastic and tends to cause a lot of distortion, especially for strong prescriptions. I'd recommend going with 1.70 if anybody's not sure which lens is best for them. To learn more about aberration, check out this blog post on highindexlenses.com: http://highindexlenses.com/abbe-number-and-color-aberration/ [...]

  2. [...] thinness, lightness, and looks. The downsides are the lenses’ optical blurriness and color aberration, the cost of the lenses, and their reflectiveness. If you are interested in getting high index [...]

  3. [...] in thickness and weight will be almost nonexistent and, in a few ways, your optics will be better. High index plastic is often assumed to be reserved for those with prescriptions so high they can see no more than [...]

  4. [...] The index of a lens is pretty much directly tied to its optical clarity. [...]

  5. BEN
    June 15, 2015 | 11:55 pm

    This site has some incredibly helpful information on it. Thanks so much for that!

    I have been wearing glasses since the age of 3 but am just now doing research of my own and not just asking my optician.

    I have extreme near sightedness and an astigmatism. i just received a new prescription and want the thinnest, but also durable lenses… Weight isn’t that much of a concern…. unless it should be.

    my current rx is -12.00+1.75×020 -15.25+2.00×165

    should i stick with looking for 1.74 or would it be wise to try 1.80 or 1.90? and what are the drawbacks of the 1.80 or 1.90 lenses?

    Thanks so much for the help!

    Ben

    • SLC
      December 15, 2015 | 12:03 pm

      As a dispensing optician, I have come across this kind of prescription a few time in practice. To be honest, our motto is very much “if it’s available in plastic, use plastic!”
      I know you say weight isn’t much of a concern, but glass lenses really are much heavier. Also consider that if you drop a glass lens on the floor, there’s a good chance it will crack or even shatter (once had a patient get punched in the eye whilst wearing them and suffered a lot of cuts to his face from the broken lenses, although i think the guy giving the punch suffered pretty badly too lol).
      However, glass lenses can be MUCH thinner, so if your main concern is how they look then give them a try. Only other thing to note is they are a touch more expensive than plastic, although you are just paying for extra thinness which you would do with plastic anyway.
      Out of interest, have you ever tried contact lenses? I know some opticians are a bit frightened of dealing with higher prescriptions, but if you get the right one to fit your contact lenses, the vision can be BRILLIANT.

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