High Index Lenses with Prism

Like most lens materials, high index lenses can be made with prism and, as would be expected, the lenses are thinner than standard lens materials.

High Index Lenses with Prism

There are positives and negatives to getting high index lenses with prism correction. The pluses are the lenses’ 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 lenses with prism, here are the things to consider:

• High index lenses are more expensive than standard lenses to begin with, but when you add on the extra charge most labs add for prism, your glasses can get really expensive. Polycarbonate or standard plastic are a better choice if you’re trying to save money.
• High index lenses with prism are thinner than standard plastic or polycarbonate lenses with prism. Prism correction, especially strong prism, is notorious for making lenses thick on one side and thin on the other. With high prism, a lens can get so thick that it could contact your face. High index can help prevent this.
• Because of their thinness, high index lenses with prism tend to be lighter than other materials.
• Thinness of your lenses helps in another way when it comes to prism: they look better. In addition to the thinner profile of the lenses, they also will distort your eyes less when you’re viewed from the outside, giving you less of the “bug-eye” or “tiny eyes” look.
• High index lenses are notorious for having a low Abbe number and, therefore, high color aberration. This means that the lenses cause blurriness, color streaking, and distortion, especially on the periphery. The thicker your lenses are, the worse your aberration is, so high index lenses with prism tend to have pretty bad aberration on one side.
• Reflectiveness of high index can be distracting regardless of whether you have prism, so if you are getting glasses in high index, it’s a good idea to get anti-reflective coating on them as well.

It’s important to weigh your options when deciding whether to get high index plastic when ordering prescription glasses with prism. Many people choose polycarbonate or plastic because they cannot deal with the optical distortion from color aberration, especially with high prism. Those who do choose high index often go with 1.67 or 1.70 because the distortion is not as bad as the distortion from higher index lenses. If aesthetics and weight are your primary concern, high index is a good option with prism, but if you are more concerned with clarity and optical precision, and you have high prism, you should look at other options.