I recently saw a health show on TV that said you should wear darker sunglasses because they filter more light. Previously, I had heard that darker sunglasses cause the pupil to open wider and make the eyes more vulnerable to harmful light; ergo, you should wear lighter sunglasses with good UV protection. I have very light colored eyes, so my eyes are especially vulnerable to harmful light anyway, which is why I really want to get this right. Can you give me a definitive answer on this one?