I am one of those people that get sunburn in the shade. I saw on TV that you can get sunburn on your retinas. I never heard of that. However, I do wear designer sunglasses anytime after sunrise and all the way to sunset. I never liked super bright light. Some people crave those bright sunny days. I like the warmth, but I have to slather on a ton of sunscreen or wear garments that cover everything. That is why I'm glad to live up north away from the beach. I went one time and got a sunburn even with coverups and sunscreen. My eyes are pretty sensitive to bright light too. I do not go anywhere without my sunglasses.
I have a pair in both of our cars, a pair in my purse and another pair of designer sunglasses on the closed-in porch. There is always a pair of sunglasses handy for me to put on. My sister had cataracts and her new lenses actually have UV light filters in them. She sort of has implanted sunglasses. I don't have cataracts and hope I never get them, but I probably would find implanted UV filtering lenses helpful. I have a pair of sunglasses with very dark lenses for those super bright days. It stops down the light to a point I am comfortable. I will even position myself outdoors so no glare sneaks in from the sides of my sunglasses.
Most people just pop on a pair of sunglasses to look cool and to shade a bit of the bright sun. For me, they are an absolute necessity. I wear them in the winter to reduce the glare from snow too. I can't take it. As a kid when I would go sled riding, I would get really snow blind after just an hour outside. Always have had sensitive eyes.