Doing away with the burden of swapping prescription glasses for a blindfold every time the sun comes out, transitional lenses—more accurately known as photochromic lenses—almost seem like magic. Indoors, the lenses are clear, but outside, they darken as if transforming into a separate pair of sunglasses, shading your eyes from seeing the sun in its bathrobe.
The keys to the transition are the UV rays of natural light. In glass lenses, the glass is embedded with crystals of silver chloride or silver halide. When exposed to UV rays, the crystals combine with the glass molecules, forming elemental silver, which appears dark compared to the clear glass. These days, however, most photochromic lenses are made of plastic. Instead of silver molecules, the lenses use an organic dye. UV rays break the chemical bonds, causing the molecules to rearrange into a form that absorbs the visible wavelengths of sunlight.
Consultation required. Not valid with insurance. Appointment required. Limit 1 per person, may buy 1 additional as gift. Limit 1 per visit. All goods or services must be used by the same person. $150 credit is for prescription glasses only. Contacts are excluded.