Spectacle Lenses of Materials Other Than Glass

Any unmounted spectacle lens made from a non-glass substrate—including CR-39 resin, polycarbonate, Trivex, or high-index plastic—belongs here. The glass heading is reserved strictly for lenses where the optical substrate is glass. Mixed or laminated constructions should be evaluated based on the essential character of the lens material.

Anti-reflective, UV, or scratch-resistant coatings applied to a plastic lens do not change its classification, provided the lens itself remains the essential article. The heading covers lenses in their finished or semi-finished state regardless of surface treatments, as long as they remain unmounted.