balhambob,
I wouldn't get too worried or worked up about it. If you have to wear spectacles to fly your medical certificate will normall require you to carry a spare pair with you. I used to wear prescription varifocal sunglasses, but for some years now I have been wearing varifocal contact lenses which I find absolutely great. I still carry my spectacles with me in my little flight bag, but it means the range of sunglasses available is much wider. I work and fly helicopters in the tropics near the equator, so I have one pair of darker lenses for really bright days and another of lighter lenses for more overcast days. I personally prefer a brown tinted lens as I find it improves visibility especially when there's a lot of dust in the air. I have a pair of Oakley Whiskers which are nice and light and with then side arms which don't affect the performance of my ENC headset too much, and my lighter lenses are Serengeti drivers gradient lenses which I have had for many years and find brilliant. I often wear sunglasses for up to 7 or 8 hours a day and find both pairs comfortable for long periods of wear.