Sun in your eyes
The scariest moments of my ride back home (40 miles of a 335 ride) were riding into the setting sun. I have a fullface helmet, prescription glasses, and magnetic sunglasses that bond to the prescription glasses. I'd used the the sunglasses during the heat of the day with no problem. I'd removed them when riding tree-shaded mountans. Replaced the sunglasses when riding through a mix of sun and shade.
I was never happy. Didn't see that well in the shade. Didn't see that well with the sun in my eyes either. Wished for my old Schuberth helmet with a sunscreen and also sunglasses.
Your solutions to this problem?