There are a lot of choices when it comes to prescription eyeglasses. Most prescription eyeglass wearers want thin and lite lenses and the choices can become overwhelming. There are basically three categories of lens materials aside from the heavier glass material. These are Regular plastic or what the industry calls CR-39. These lenses are OK for very low prescriptions however they do not protect you 100% from UVA and UVB. Plastic lenses can have a UV filter added but the protection will lesson over time. The next category is what is considered a mid index. These lenses are not used often anymore and are an economical alternative to higher index. The last category is high index which have varying degrees of thinness. The higher the index number the thinner the lens. Another popular lens material is Polycarbonate which is always recommended for children because of the impact resistance that it provides. All high index lenses have UV built into them. Below is a recommendation on which lens material to use with your prescription.
+1.00 to -1.00 Plastic will be OK
+2.00 to -2.00 and above High Index should definitely be considered
***Children should always use polycarbonate
There are many different brand names for these materials but to simplify the selection lenses can really be broken into these three categories. Polycarbonate is a economical way of purchasing thinner and lighter lenses but are still thicker than some of the higher index lenses such as the 1.74 high index, which would be the thinnest lens and flattest lens available.