Flying in Florida quite alot it is essential to wear sungflasses when flying. The 'macclea', think i have spelt that right, is the tiny patch on the back of the eye that allows you to see detail, it degenerates rapidly with UV exposure and there is alot of that when flying (eating greens provides lutins which protects the macclea). The majority of the eye retina is used for peripheral vision.
Bearing that in mind, despite shortterm blinding headaches, it is really essential for a pilot to protect his/her eyes with good sunglasses.
I spent quite a long time choosing the right pair and have used Randolphs which as other say are great. I have settled on a pair of Oakleys Whiskers which are purpose built for flying as ear piece fits under headset without breaking seal and lens iridium coated to cut out glare. I bought the black frames with darkest lens. They are one of my prized posessions and recomend them fully.