High Index Lenses

High Index Plastic Vs. High Index Glass Lenses

People who have heard of high index glass and high index plastic lens materials may wonder which is better for them.

Each material has its strengths and its weaknesses, and what may be right for one person will not be right for everybody. If you are deciding between high index glass and high index plastic lens materials, it is important to consider impact resistance, scratch resistance, lens thickness, aesthetics, and frame choice. Here is a list of some important differences between high index plastic lenses and high index glass lenses:

• High index plastic is much lighter than high index glass, even though high index glass lenses are often thinner.
• High index glass lenses are going to have the highest index. This means that they will be thinner than high index plastic, but they may also have some optical problems such as color aberration.
• High index plastic is less likely to crack when dropped. High index glass lenses tend to be very brittle and to break easily.
• High index glass lenses have a very low Abbe number, meaning that they cause optical abnormalities like color aberration (blurring of colors), especially in your peripheral vision. Aberration happens, to an extent, with every high index material, but it is worst with glass. 1.70 high index plastic is generally agreed to have the best balance between thinness and optical clarity.
• Glass lens material is not suitable for rimless or half-rimmed frames. For them, you will need a form of plastic.
• High index glass lenses are going to look better from the outside, especially for very strong prescriptions. Since they are the thinnest lenses, they will cause the least eye distortion from an outside perspective. It’s important to note that the difference here is only noticeable on very strong prescriptions.
• High index glass and high index plastic both require anti-reflective coatings to get the most out of their optics. They are both very reflective.

If you are still wondering whether to go with glass or plastic, it is a good idea to read some of our other posts which focus on specific materials within either category. Keep in mind that most people go with plastic and are happy with it; high index glass is a rare and expensive lens. There are those who prefer it, though, so if you are unsure, it is a good idea to do some more research and really weigh your options. Weight and thinness are the biggest things to consider when deciding between high index plastic or glass, with brittleness following close behind. Hopefully this helps you in your decision, and thanks for reading!