Eye protection is vital for most outdoor activities, especially cycling as debri and spray from the road can be flicked up into your face. A pair of good quality sports sunglasses will help to keep the wind, insects, rain, spray and dust out of your eyes. Dark ones will cut down on light so you don't have to squint to see where you're going. All glasses should eliminate harmful UV rays, protecting your retinas from damage. So that you can protect your eyes in all conditions, glasses with interchangeable lenses are useful. Either that, or get yourself one pair for bright, dull and dark light conditions.