I always wear raybans during the day under my Full Face helmet , stops the glare , & doubles up a eye protection
Worst experience i have seen was a Biker being taken out by a pheasant flying across a country road at low level, hit him straight in the face, smashed his Visor & he went down in a ditch, fortunately apart from a few scars around the nose & some bruising he was OK, bike was pretty smashed up though