Shooting glasses and safety eyewear. Worth wearing for the ricochet and the clay fragment as much as anything else — and the right lens genuinely helps you see the target.
Lens colour, roughly: yellow and orange lift contrast in flat or failing light and make an orange clay jump off a grey sky; smoke and grey cut glare on bright days; clear is for low light and for pure eye protection indoors or on a dull evening.
Sets with interchangeable lenses — the Eyelevel Marksman 5-in-1 and the Jack Pyke Pro-Sport with four lenses — cover changing conditions in one case, which is usually the sensible buy if you shoot year round.
Walker's and Bollé cover the rest, including Bollé's safety-rated Tracker and Silium+.
See also hearing protection and hearing and eye protection.