The lens material is one of the most important considerations in buying children's glasses. The most common materials are: plastic, high index plastic, polycarbonate and glass. Glass is the heaviest but scratches the least; however, it shatters into very small pieces if broken. Therefore, it is not very safe and not prescribed much. Plastic is common, relatively thin and relatively safe. High index plastic is the thinner and lighter version of regular plastic and is also used often. Polycarbonate is a material that is also thinner and lighter and is the most impact resistant material available. It is used frequently in safety items such as helmets.
For those safety reasons, polycarbonate is the lens material of choice for kids' glasses. They are difficult (but not impossible) to break and if they do break, the pieces tend to be bigger and fall away from the eyes. Because of kids' active lifestlyles and liability reasons, most offices will prescribe only polycarbonate for kids.
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