We do a fair number of prescription lenses for both the aviator sunglass frames we sell, or for other sunglass frames our customers send to us. The most common question I get asked is about prescription lens materials. Many of our customers are pilots, so they are looking for aviator prescription sunglasses. So, lets discuss this important issue. Lens Materials The very first prescription lenses were made out of glass. People got very comfortable with glass lenses despite their weight because of the distortion free feature of glass. So, for a very long time everyone wanted glass lenses, but over time glass became less popular because of it's weight on the nose. Today, there are more choices, but sometimes it is hard to choose. Prescription lenses can be made from a number of different materials. The most common are: Polycarbonate Trivex CR-39SRC Plastic Crown Glass Each material has a set of properties that should be considered when deciding which lens material to use in your prescription lenses. Lets discuss lens properties first. Len Properties The most important lens properties are these: Refractive Index Abbe Value The Refractive Index of a lens is an indicator of how well the lens material bends light. For a given prescription lens power, a lens made of a material with a high refractive index will be thinner than a lens made of a material with a lower refractive index value. The refractive index of most popular prescription lens materials range from 1.498 (CR-39 plastic) to 1.74 (a type of high-index plastic). The higher the Refractive Index number the better the lens. If you want more information about Refractive Index you can find it here: "Index of Refraction". Abbe Value is a measure of the lens material's dispersion of light. A lens with a low Abbe Value can lead to chromatic abberation (which causes colored halos around lights). Abbe values of prescription sunglass lenses range from a high of 59 (regular glass lenses) to a low of 30 (polycarbonate lenses). The higher the Abbe Value the better the lens. If you want more information about Abbe Value you can find it here: "Eyeglass Lens Materials". So I have made the following chart showing Abbe Value and Refractive Index numbers for you. Comparing Lens Materials Lens Material: Refractive Index: Abbe Value: Polycarbonate 1.586 30 Trivex 1.54 45 CR-39 Plastic 1.498 58 Crown Glass 1.523 59 As usual, the perfect set of values for both properties don't ever line up! So, what to do? How Do You Use Your Sunglasses? Glass lenses can break and cause serious injury to your eyes, and combined with the weight make them a concern for most people. For children and sport shooting enthusiasts polycarbonate lenses work well because they are lightweight and significantly more impact resistant than glass. Trivex lenses are lightweight, impact resistant and scratch resistant making them a good choice over polycarbonate lenses. Plastic CR-39 lenses were first developed in the 1940s and are about 1/2 the wieght of glass lenses. They have excellent optical qualities and are more impact resistant than glass. The biggest concern most users have is whether or not they scratch easily. In our store we sell CR-39SRC lenses which have a factory applied scratch resistant coating applied to them. How To Order Prescription Aviator Sunglasses It is important to know that when you get your eye examination the eye doctor is required to give you your prescription. The eye doctor can not withhold your prescription making you order your prescription sunglasses from them. You can find a blog post on our website on how to order aviator prescription glasses at "Order Prescription Aviator Sunglasses". My Recomendation The lens thickness is certainly important because of the weight of the frame with the lens on your nose bridge can be uncomfortable. The majority of my customer choose CR-39SRC (with a factory Scratch Resistant coating) plastic lenses as the best option, and that is what I use for my own prescription lenses. I have worn these CR-39SRC plastic lenses for as long as I can remember, and they have served me well. Trivex lenses are also popular, but today the supply of Trivex lenses is poor due to world production shortages. CR-39SRC is readilly available. As I mentioned earlier, crown glass lenses are very heavy compared to these other materials. But, in the end, the choice is up to you. CR-39SCR Prescription Lenses Now that you have all of the information you need you can order your prescription lenses right here on our website. Simply go to: "Prescription CR-39SRC Lenses" and find the option you would like. Until next week keep your eyes safe with a great pair of aviator sunglasses! ps: Please share "Prescription Sunglasses For Pilots" with your friends on social media.