Polarized lenses

Lenses can be polarized but the polarization seems to be on the outside of the lens and can come off. One thing that will cause it to come off is cleaning with alcohol. There may be other causes. That one I know.



Question: Is polarization always on the outside of the lens? Or can it be built into the lens so that it would not wear off? If it can be built into the lens, do you know anyone who makes sunglasses like that?



Thanks.

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