Fl-41 is the tint most commonly recommended by doctors and specialists for the prevention of light sensitivity and migraines. One study found that the use of Fl-41 glasses reduced the number of migraines by an average of 74% in a four month period. Fl-41 glasses are also effective at reducing photophobia and light sensitivity that does not result in migraines, particularly light sensitivity caused by florescent lighting and computer screens. Fl-41 lenses block 80% of the blue wavelengths that can trigger eye pain, dizziness, and headaches. Though these glasses are primarily intended for indoor use, our Fl-41 glasses are suitable for both indoor and outdoor use, blocking 99% of harmful UV rays. Free carrying case and microfiber cleaning cloth included.