8 minutes well spent if you want a primer on ophthalmic lens materials.

Incidentally, the Abbe number is why I always wear glasses with small lenses positioned very close to the eyes: chromatic aberration affects smaller lenses less. The shape and size of the lenses in the frames you choose is something to consider when you determine the kind of material you want the lenses made out of with your optician.

The video does mention that glasses made for children in the US are almost always made of polycarbonate to avoid litigation in case of a lens shattering during a child’s activities. This is specific to the US: polycarbonate is almost never considered in any other country because it is a material with really poor optical properties.

If you’re in the US, I urge you to resist fitting your child with polycarbonate lenses: a child’s vision is still developing and it really deserves better. CR-39 is a minimum. Or if you have a bit more disposable, I personally recommend Trivex: it’s impact-resistant too, but it’s optically better, it’s lightweight and it naturally has UV protection without coating.