Today, not many people buy lenses actually made of glass. They’re heavy and not as impact-resistant as other lenses (and could cause serious eye injury if they break). Here’s a guide to lens choices and coatings you might be offered—and when to refuse them. For example, many lenses come with scratch-resistant protection or coatings that help block harmful rays, so you shouldn’t pay extra for those. Prices can vary widely, so talk with your eye doctor and optician about what’s best for you. Also ask what warranties the manufacturer offers for features you’re considering, in case the lenses have to be redone or changed.